If your Mac restarts unexpectedly or displays a message that it restarted because of a problem, note when it happens and which apps were open. Software and connected devices can both be involved, so changing one thing at a time is more useful than immediately erasing the system.

Work through these checks in order

  1. Install available macOS and relevant app updates, then watch for a repeat. If the problem began after installing an app or extension, check with its developer for an update.
  2. Shut down the Mac and disconnect nonessential peripherals such as hubs, drives, and printers. Leave only essential equipment connected and use the Mac to see whether the restart recurs.
  3. If disconnecting devices stops the issue, reconnect them one at a time and test after each one to identify a device or cable that brings the symptom back.
  4. Try starting the Mac in Safe Mode to help isolate software that loads at startup. If behavior changes in Safe Mode, review recently added apps and extensions.
  5. If the Mac still restarts after updates and peripheral checks, run Apple Diagnostics for your model and record any result or reference code before contacting service.

When to get more help

If the Mac restarts in a loop, cannot reach the desktop, shows unusual heat or sounds, or Apple Diagnostics reports an issue, contact Apple Support or a service provider. Reinstalling macOS should follow a backup and guidance appropriate to the symptom.

Have an Apple device assessed before upgrading

Considering selling or upgrading your Mac? Makaiteetum can assess your Mac or other Apple device before you decide. Call 064-564-7945 or contact Line @KunTum.

References

Apple Support’s guidance for unexpected Mac restarts: