PowerEdge r610 Died

Yesterday when I tried to log into one of our r610 servers, I found that it was powered off.  I tried the power button, and it didn't respond even though the power supplies had green lights.  I then tried unplugging the server for about 30 seconds.  When I plugged it in, it did power on, and I was able to log in.

However, I need to know why it was powered off.  I checked the logs, and all I can tell is that it stopped logging sometime between 7/17/2016 and 7/24/2016.  No users logged in in that time frame.  No indication why it was powered off.