Windows Update Server and Virtual Machine Standard

Turn Off Automatic Restart

In Advanced options, scroll down to “Notify me when a restart is required to finish updating.” **

Make sure this is ON.
This forces Windows to ask first instead of auto-restarting.
If you see a “Restart automatically” toggle, turn that OFF.

** “Show a notification when your device requires a restart to finish updating” is the same thing as “Notify me when a restart is required.”

It’s just the new phrasing since Windows 10 build 1903 and up through 11.

Settings → Windows Update → Advanced options

Scroll down to the section called Notifications or Update notifications
Make sure “Show a notification when your device requires a restart to finish updating” is turned ON

If that toggle’s on, and you’ve set your update policy to notify to install or no auto-restart with logged-on users, the server should not reboot itself without user interaction.