At home I have a Dell PowerEdge 2900 III running VMware ESXi 5.5U2. I have had this server for over 3 years and it has been rock solid. The last few days it seems to be restarting itself for no reason, and when I log into the vSphere client I don't see any alerts except for ECC corrected some errors on one of the sticks of memory, but that alert has been there for months with no issues. At first I thought maybe it was a power issue because my battery backup recently notified me that the battery needs to be replaced, but I have another server and a switch plugged into the same power source and they are unaffected; I also have the second power supply plugged into a different power source.
Not quite sure how to pull logs from ESXi, or why the server would just randomly reboot.