I have an HP ProLiant DL380p Gen8 that is running VMWare ESXi 5.5. It has been rebooting itself at seemingly random intervals for the past 24 hours. There is only a single VM running, and even if I shut it down the host will still reboot. The server is not running out of memory or disk space, and as far as I can tell is not overheating. I've tried looking through log files, but there is just so much to look at.
What are the most important steps in diagnosing this problem (including which settings to check, what files to look at, what specific message would indicate trouble, should I start pulling memory, is there a diagnostic CD that does all this for me, etc)?
I know this is a very broad question. I'm happy to provide log files if necessary to make this more specific to my situation.