iMac reboots or logs out overnight since Yosemite 10.10.2

Every morning since the Yosemite 10.10.2 update my mid-2011 iMac (12 GB RAM, Yosemite update over Mavericks over Mountain Lion over Lion) wakes to the login screen and I have to log in then sit through a reboot. I should just have to clear the screen saver.

For the first few days after the update the situation was more bizarre every morning. The computer only partially rebooted. Fixed after running Onyx and unchecking a few of the Login Items I did not need, but left with this situation now.

Energy Saver settings:
Computer sleep never.
Display sleep 15 minutes.
Unchecked all three of put hard disks to sleep, wake for network access, start automatically after power failure and unchecked both of the schedule options.

At least the other Yosemite problems I had been having have now been fixed and the iMac runs well, other than this issue.

Any thoughts?
Thanks.

I think I found it: System Preferences, Security & Privacy, "Log out after __ minutes of inactivity". It was set to less than 24 hours. Maybe I had set it to longer than that and then the Yosemite update reset it to a lower number? Will found out tomorrow morning.

Just remove the check from the box and you won't have to worry about it. It's under advanced options anyway which will require your admin password.

chscag said:

Just remove the check from the box and you won't have to worry about it. It's under advanced options anyway which will require your admin password.

Click to expand...

Thanks, should have mentioned I did that.