A Mac that repeatedly restarts during startup is usually experiencing a software conflict, a problem with startup data, an incompatible peripheral, or a hardware or storage failure. Disconnect accessories, try Safe Mode, install available macOS updates, and use macOS Recovery to repair the startup disk or reinstall macOS without erasing your files.
Follow the steps below in order. Stop when the Mac starts normally.
Quick Answer
- Disconnect all nonessential accessories and try starting the Mac again. 2. Start in Safe Mode. If the Mac works there, remove recently installed software, login items, or system extensions. 3. Install macOS updates and remove recently connected hardware or newly installed apps. 4.
Disconnect Accessories and Perform a Normal Restart
A damaged cable, external drive, hub, display adapter, or other USB device can interfere with startup. Before changing system settings, remove this possible cause.
- Shut down the Mac. If it is stuck in a restart loop, press and hold the power button until it turns off.
- Disconnect everything except the power cable, display, keyboard, and mouse or trackpad. Remove external drives, USB hubs, printers, cameras, memory cards, and other accessories.
- Wait about 30 seconds.
- Turn on the Mac.
If it starts normally, reconnect accessories one at a time and restart after each connection. The device that brings back the problem may need a different cable, a software update, or replacement.
If the Mac still restarts, continue with Safe Mode.
Start the Mac in Safe Mode
Safe Mode starts macOS with limited software and performs some startup checks. It can help identify problems caused by login items, third-party extensions, or recently installed software.
The startup procedure depends on whether your Mac has Apple silicon or an Intel processor. If you are unsure which type you have, try the Apple silicon method first. If it does not match what you see, use the Intel method.
Apple silicon Mac
- Shut down the Mac.
- Press and hold the power button until Loading startup options appears.
- Select a startup volume.
- Press and hold the Shift key, then click Continue in Safe Mode.
- Sign in. You may need to sign in again after the first login.
Intel-based Mac
- Shut down the Mac.
- Turn it on and immediately press and hold the Shift key.
- Release the key when the login window appears.
- Sign in. You may be asked to sign in a second time.
If the Mac starts in Safe Mode, restart it normally. If normal startup works afterward, the issue may have been temporary. If the restart loop returns, remove possible software causes.
Remove login items and recently installed software
Warning: Removing an app or login item can change how you work, and uninstalling software may delete its settings. Make sure you know what you are removing. Save any open work first.
In Safe Mode:
- Open the Apple menu and choose System Settings.
- Click General, then click Login Items & Extensions.
- Review the items under Open at Login and remove recently added or unfamiliar items with the minus button.
- Review extensions, especially those installed by antivirus tools, VPNs, disk utilities, device drivers, or virtualization software. Turn off or remove an item only if you recognize it and know it is not required.
- Open Applications in Finder and move recently installed apps to the Trash if they are strongly associated with the problem.
- Restart normally.
On older versions of macOS, login items may be under Users & Groups in System Preferences.
If a particular app, driver, security tool, or peripheral utility was installed immediately before the restart loop began, check the developer’s instructions for a current version or a complete uninstall procedure. Avoid deleting random files from system folders.
For step-by-step startup instructions, see this guide to starting a Mac in Safe Mode.
Install macOS Updates
A startup loop can result from a bug that has already been addressed in a macOS update. If you can reach the desktop, install available updates.
- Open the Apple menu and choose System Settings.
- Click General, then Software Update.
- Install any available macOS update.
- Restart the Mac when prompted.
On older macOS versions, open System Preferences and click Software Update.
Keep the Mac connected to power during the update. Do not force it to shut down while the installation is in progress. If it cannot remain on long enough to complete an update, continue to Recovery.
Reset NVRAM on an Intel Mac
NVRAM is a small area of memory that stores certain settings, such as startup disk selection, display behavior, and sound volume. Incorrect startup settings can occasionally contribute to boot problems.
This procedure applies to Intel-based Macs. Apple silicon Macs manage these settings differently and do not use the same manual NVRAM reset process.
Warning: Resetting NVRAM may return some settings to their defaults. You may need to reselect the startup disk or adjust display, sound, or other preferences. It does not erase personal files.
- Shut down the Mac.
- Turn it on and immediately press and hold Option-Command-P-R.
- Continue holding the keys for about 20 seconds.
- Release the keys and allow the Mac to start.
Some Intel Macs may appear to restart during this process. If the Mac continues looping, move to macOS Recovery. For background and model-specific considerations, see this explanation of NVRAM and why resetting it can help.
Start macOS Recovery and Run First Aid
macOS Recovery provides tools for repairing the startup disk, reinstalling macOS, and restoring from a backup. Start with Disk Utility to check the disk’s file-system structure.
Open macOS Recovery
Apple silicon Mac
- Shut down the Mac.
- Press and hold the power button until Loading startup options appears.
- Click Options, then click Continue.
- Select an administrator account if asked and enter its password.
Intel-based Mac
- Shut down the Mac.
- Turn on the Mac and immediately press and hold Command-R.
- Release the keys when the Apple logo or a spinning globe appears.
- Join a Wi-Fi network if prompted, then select an administrator account and enter its password.
If Command-R does not open Recovery, try again with the keyboard connected directly to the Mac rather than through a hub. An Intel Mac may also offer Internet Recovery with Option-Command-R, which loads Recovery tools over the internet.
Run First Aid
- In the Recovery window, choose Disk Utility, then click Continue.
- Choose View > Show All Devices.
- In the sidebar, select the lowest-level internal volume that appears under the internal physical drive.
- Click First Aid, then click Run.
- Repeat First Aid for other internal volumes, the container, and finally the physical internal drive, moving upward through the sidebar.
The names and structure may vary. Do not run First Aid on an external drive unless you intend to check that drive.
When the checks finish, quit Disk Utility and choose Restart from the Apple menu.
What First Aid results mean
If Disk Utility reports that the volume appears to be OK, the restart loop may be caused by damaged system files, incompatible software, or hardware that is failing intermittently. If First Aid reports that it repaired errors, restart and test the Mac.
If First Aid cannot repair the disk, do not repeatedly erase or reformat it while trying to preserve data. If possible, back up important files using another Mac, a backup system, or a professional data-recovery service before taking additional steps.
Reinstall macOS From Recovery
Reinstalling macOS replaces system files while generally preserving personal files, apps, and settings. It is useful when the operating system is damaged but the startup disk is still usable.
Warning: Reinstalling macOS is not a substitute for a backup. Although the standard reinstall option is designed to preserve data, unexpected disk or hardware problems can cause data loss. Do not erase the disk before reinstalling unless you have a reliable backup and intentionally want to remove everything.
- Start macOS Recovery.
- Choose Reinstall macOS, then click Continue.
- Follow the onscreen instructions.
- Select the current macOS startup volume when asked.
- Keep the Mac connected to power and connected to the internet.
The installation may take a while and the Mac may restart several times. Do not interrupt it unless it is clearly frozen for an extended period.
If the installer does not show the internal disk, returns an error, or the Mac restarts during installation, the problem may involve the internal storage, firmware, or another hardware component.
If You Can Reach the Desktop Briefly
If the Mac stays on long enough to use it, back up important files immediately before more troubleshooting. Use Time Machine or copy critical documents to another storage location. Do not assume that a Mac that starts successfully once is fixed.
You can also check for recent changes:
- Apps installed or updated shortly before the issue began
- Antivirus, VPN, backup, cleaning, or disk-management utilities
- Printer, audio, graphics, or other hardware drivers
- External drives that were connected during the first failed startup
- Login items and background processes added recently
Remove or update one suspected item at a time, restarting after each change. This makes it easier to identify the cause.
Troubleshooting
The Mac restarts before Safe Mode appears
Disconnect all accessories and try again. For an Intel Mac, verify that you press Shift immediately after turning it on. For an Apple silicon Mac, hold the power button until startup options appear, then hold Shift while selecting the startup disk.
If the Mac cannot enter Safe Mode or Recovery, try a different keyboard if available. A failing keyboard, wireless connection, or USB hub can prevent startup shortcuts from registering.
The Mac restarts only when an external drive is connected
Disconnect the drive and start the Mac. If startup succeeds, do not use the drive as a startup disk until you check it. Connect it after macOS loads and run First Aid on the external drive from Disk Utility.
A failing external drive can cause long delays, freezes, or restarts. Copy important data from it as soon as possible.
First Aid reports that the disk cannot be repaired
Back up or recover important data before erasing anything. If the disk is an older hard drive, repeatedly failing, or missing from Disk Utility, hardware failure is a serious possibility. An Apple Authorized Service Provider can test the storage and determine whether repair or replacement is needed.
The Mac restarts after reinstalling macOS
Disconnect accessories again and test the Mac with only essential equipment connected. If the restart continues on a clean system, software is less likely to be the cause. Possible causes include defective memory, storage, logic-board components, overheating, or power problems.
The Mac shows a kernel panic message
A kernel panic is a serious system-level crash that can force a restart. Note the exact message if one appears and think about recently installed drivers, extensions, or hardware. Remove third-party system software and test in Safe Mode. If panics continue after macOS is reinstalled, seek professional service.
When to Contact Apple Support
Get help if:
- The Mac cannot open Safe Mode or macOS Recovery.
- Disk Utility cannot see or repair the internal drive.
- The Mac restarts during a clean macOS installation.
- You hear unusual sounds, smell burning, or notice excessive heat.
- The problem began after liquid exposure, a drop, or another physical event.
- The restart loop continues with no accessories and after reinstalling macOS.
If you have a backup, bring its details and any recent error messages to the appointment. Avoid repeated forced shutdowns when the Mac is attempting a disk repair or system installation.
Frequently Asked Questions
Can a low battery cause a Mac to keep restarting?
Yes. An inadequate charger, damaged cable, loose connection, or failing battery can cause power interruptions. Connect the Mac directly to a known-good power adapter and outlet, then try again.
Will Safe Mode delete my files?
No. Safe Mode does not intentionally delete personal files. It limits startup software and performs system checks, but you should still save work before troubleshooting.
Does reinstalling macOS erase everything?
A standard Recovery reinstall is intended to preserve personal files, apps, and settings. However, no reinstall is risk-free when the disk is damaged. Do not choose erase or reformat options without a verified backup.
Should I reset the System Management Controller?
The procedure depends on the Mac model, and Apple silicon Macs handle power management differently from Intel Macs. First disconnect accessories, test the charger, use Safe Mode, and open Recovery. If the issue appears power-related, Apple Support can provide the correct model-specific steps.
Why does the Mac restart after I enter my password?
This often points to a login item, background extension, corrupted user environment, or system-level software that loads after authentication. Test Safe Mode and remove recently added login items or utilities.
Final Thoughts
Start with the least disruptive fixes: disconnect accessories, test Safe Mode, remove recent startup software, and install updates.