PC rebooted overnight

Hi Rich,
You have already selected the correct notification settings. However, “Notify me when a restart is required” does not prevent an eventual automatic restart. Windows 11 can still restart outside the 18-hour active-hours window.
Also, “Get the latest updates as soon as they’re available” is unrelated to restarting. It simply provides non-security fixes and feature improvements earlier. You may leave it on or turn it off.

First confirm that Windows actually restarted​

Closed applications alone do not prove there was a reboot.

1. Open Start.
2. Type reliability.
3. Select View reliability history.
4. Select the column corresponding to last night.
5. Look for Windows Update, Windows was not properly shut down, or an application failure.

Also check:

1. Open Settings.
2. Select Windows Update.
3. Select Update history.
4. Check whether an update was installed overnight.

Recommended settings​

1. Open Settings > Windows Update > Advanced options.
2. Leave Get me up to date turned Off.
3. Leave Notify me when a restart is required to finish updating turned On.
4. Open Active hours and select Manually.
5. Set the 18 hours to cover the period when an unattended restart would be most disruptive.
6. When Windows Update displays Restart required, open Windows Update and choose Schedule the restart.

Windows 11 should display a toast notification and may also put a restart/update indicator in the notification area. Unlike older Windows versions, however, the indicator is not guaranteed to remain permanently visible until you act.

If the PC has Windows 11 Pro​

There is a Group Policy named No auto-restart with logged on users for scheduled automatic updates installations, but Microsoft warns that it does not always behave exactly as its name suggests and could leave updates awaiting a reboot indefinitely. I would use it only if the normal notification arrangement proves insufficient.

1. Create a restore point first.
2. Press Windows + R.
3. Enter gpedit.msc and press Enter.
4. Navigate to Computer Configuration > Administrative Templates > Windows Components > Windows Update > Manage end user experience.
5. Open Configure Automatic Updates.
6. Select Enabled.
7. Choose 4 – Auto download and schedule the install.
8. Enable No auto-restart with logged on users for scheduled automatic updates installations.
9. Restart the computer once manually.

To undo this, set both policies back to Not Configured.
Do not use registry edits or disable the Windows Update service for this. Those approaches can interfere with security updates and Windows may recreate the settings anyway.
The important first step is checking Reliability History. If there is no Windows restart entry, one or both applications probably closed or crashed independently.