I came home one day and my workstation was shutdown. Hmm.
Booted it up, and 2 minutes later...Shutdown.
Booted into BIOS and watched the CPU temp go from 20C to 106C and shutdown in less than a minute.
The internet said it was bad Thermal Interface Material or Heatsink gone bad.
Replaced then and we're back online!
I installed lm_sensors so I could monitor from the OS: