I've been experiencing mysterious reboots on my machine and another 10.12 lab machine. I can't find any entry in policy logs, system logs, jamf logs, or anything like that. The machines will just be back at the login prompt, but not any reports of a bad shutdown or anything. I've noticed it's also only when I've walked away from the machine for a bit (lunch, meetings, etc). I can't seem to find anything that would be causing it. Any ideas where to look or what to look for?
If you look in System Information in the Managed Preferences section, is there any auto log out setting present? We had a mysterious "rebooting" issue that turned out to be a config profile that was applying a 30-minute automatic logout.