iMac shuts down after five minutes

If your iMac is shutting down after five minutes, there could be several potential reasons for this issue. Here are some troubleshooting steps you can follow to diagnose and possibly resolve the problem:

1. Check for Overheating: Overheating is a common cause of sudden shutdowns. Ensure that the iMac is placed on a flat, well-ventilated surface, and check if the cooling fans are working correctly. Clean any dust or debris that may be obstructing airflow.
2. Update macOS: Make sure your iMac is running the latest version of macOS. Software updates often include bug fixes and improvements that may resolve such issues.
3. Check Energy Saver Settings: Go to System Preferences > Energy Saver and ensure that the settings are configured appropriately. Look for any options related to sleep or automatic shutdown and adjust them if needed.
4. Check for Kernel Panics: If your iMac encounters a critical error, it may shut down automatically to prevent further damage. Check if there are any kernel panic logs by going to Applications > Utilities > Console > System Reports > CrashReporter. Look for any recent logs indicating kernel panics.
5. Reset SMC: Resetting the System Management Controller (SMC) can sometimes resolve power-related issues. To do this, shut down your iMac, unplug it from the power source, wait for 15 seconds, and then plug it back in. After a few seconds, turn on your iMac.
6. Check for Software Conflicts: Some third-party applications or drivers can cause conflicts that lead to shutdowns. Try booting your iMac into Safe Mode (hold down the Shift key during startup) and see if the problem persists. If it doesn't shut down in Safe Mode, the issue may be related to software conflicts.
7. Check Hardware Connections: Ensure all cables and connections are secure, including power, peripherals, and any external devices.
8. Run Apple Diagnostics: Apple Diagnostics can help identify hardware issues. Restart your iMac, and during startup, hold down the D key until the Apple Diagnostics screen appears. Follow the on-screen instructions to run the diagnostics.
9. Monitor Activity Monitor: Open Activity Monitor (Applications > Utilities > Activity Monitor) and check for any processes consuming excessive CPU or memory resources. This could indicate a software-related issue causing the shutdowns.

If you have tried the above steps and the problem persists, it's recommended to contact Apple Support or visit an Apple Authorized Service Provider for further assistance. They can diagnose and repair any potential hardware issues with your iMac.

A couple things you can try…

Reset the SMC of your Mac - Apple Support

Reset NVRAM on your Mac - Apple Support

The screen saver has nothing to do with your iMac shutting down. How old is it?

Check "About This Mac" under the Apple menu for the model date.