Event ID 6008 is logged in the System log

all windows event id
support.microsoft.com/kb/950323/en-us

Note This event indicates that the system was shut down unexpectedly. This event is incorrect because the system was successfully shut down.

The Event Log service periodically updates the last alive time stamp that is stored in a registry entry. The Event Log service cleans the last alive time stamp during system shutdown. This time stamp is not cleaned after an unexpected shutdown (dirty shutdown). Then the next time that the system starts, the Event Log service raises an event to report the unexpected shutdown.

However, a race condition may occur between the timer thread and the system shutdown thread. The last alive time stamp may be reupdated after it is cleaned during system shutdown. Therefore, an "unexpected shutdown" event is reported incorrectly.  

Windows Server 2003 Random Shutdown with Event ID 6008
Monitor the CPU temprature. 
Consider to control the dissipation of the heat in the CPU and GPU
Or the Power Supply Unit