Unexpected Shutdown

Hey Everyone,

I have a proxmox server running for about 2 years now. Recently the server has been shutting down and not rebooting. Usually if power fails the server reboot and functions properly. In the past week it has gone down 3 times with no explanation and has to be manually started up again. I have checked the web ui system logs to no avail.
Any advice on how to troubleshoot this behavior.

thanks