After update Mac won’t restart

Q - " After update Mac won’t restart "

A - After update as Monterey 12.3 to Monterey 12.3.1?

A - After upGrade from macOS ?? to Monterey 12 ?

A - Either way, Suggest restarting in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal.

What is status of the Mac? Does screen show anything? Any signs of life>

Can you boot to Recovery? How to is covered here:

How to reinstall macOS - Apple Support