Mac shutting down for no reason, and unable to restart for some time.
iMac 27″, macOS 12.6
iMac 27″, macOS 12.6
There might be an issue with your startup disk.
Have a kook at the troubleshooting in this related article:
If your Mac starts up to a circle with a line through it - Apple Support
Mac shutting down for no reason, and unable to restart for some time.