You should try booting the system in safe mode using the F8 option during the boot up process. You should also consider disabling the auto restart within the same window. This way you will see the screen with the error long enough to see what the issue could be.
I.e. if it deals with an DLL/missing ntkrnl etc. YOu could try to recover to the last known good config. or run a repair install of the OS. It may indicate that there is an issue with memory/device etc.
You could use the Lights Out Management to see whether the server is reporting hardware failure events.
