The only way I've found to REALLY work, which has actually prevented these unattended restarts, is to disconnect internet physically from the computer when I'm not sitting at it. I make sure that no WiFi can connect automatically and I pull out the ethernet cable. I've done this for months now with stable results (No restarts).
Last night I had to do a backup transfer to one of my cloud services, so I had to leave internet connected overnight. And wouldn't you know it - Windows found out and restarted during the backup, which corrupted all the files on the cloud service!
Why was this a design choice you made? How is this user friendly in ANY way? I know companies who've lost MILLIONS because of this, technicians who've lost their jobs because there is no STABLE way to know for sure when or how the system will reboot. The lack of response from Microsoft is just utterly irresponsible.
This issue walks hand in hand with the deepthroathing "feature" that is telemetry. When enough people has lost their work, there is no way back from this - and the switch cost will be endlessly low. No wonder Apple can charge premium when people just look for a way to control when they can reboot. SERIOUSLY microsoft, this has to stop, NOW.