You come back to your Mac and see a message saying it restarted because of a problem. It is alarming, but Apple says this is rare and usually traced to software installed on the Mac or to devices connected to it. The fix is to check software first, then hardware.
Step 1: Check your software
- Install all available updates. Open System Settings, General, Software Update.
- Act on the app prompt. If your Mac suspects an app caused the restart, it might ask if you want to move that app to the Trash. Apple says to click Move to Trash and then contact the software developer to see if an update is available.
- Try safe mode. Apple suggests using safe mode to try to isolate the cause.
- Reinstall macOS if nothing else works. Back up first. See our Time Machine guide.
Step 2: Check your hardware
- Shut down your Mac and disconnect all peripherals such as hard drives and printers. On a desktop Mac, leave only the display, keyboard and mouse or trackpad.
- Turn the Mac on and use it for as long as it usually takes for an unexpected restart to occur.
- If the problem stops, connect devices one at a time, testing after each, until it comes back. That device is the culprit.
- If disconnecting devices does not help, use Apple Diagnostics with the devices disconnected.
What if it restarts every time?
Apple warns that if the problem makes your Mac restart every time it tries to start, it might eventually shut down. In that case see our guide to fixing a Mac startup problem.
A cause people overlook
A new accessory or app is the most likely trigger, so think about what you added shortly before the first restart. That is common-sense advice rather than something Apple lists in this exact form.
Frequently asked questions
Is this a virus?
Apple points to software and connected devices as the usual causes. See do Macs need antivirus for more.
Can an update cause it?
Software issues are a listed cause, and installing available updates is Apple’s first step.
Sources
Last checked November 3, 2026. Apple changes its instructions between updates, so if a menu looks different on your Mac, check the linked Apple page.
