Install temperature monitor software like CPU HWMonitor to check what your CPU temperature is. Also verify that your CPU fan is working.
Reboot your PC and log into BIOS. Check what the alarm temperature is for your CPU, and look at the temp + fan speed reading shown in BIOS.
If you have a normal desktop PC, open up your case, clear out the dust, switch on the PC with the side panel off, and verify that your CPU fan works.