If you can boot up into the BIOS it should display them in some part of it.
While you are in the BIOS also check the voltages as a failing PSU can also cause problems.
The 3.3, 5 and 12v should be within Plus/Minus 5% of their value.
There is a program that you can download, but if it's freezing and shutting down, then that will be a no go.
If the fans are going full bore, that will be a definite clue, depending upon how long the machine runs for before it shuts down.
The program is the free Version of HWMonitor -
http://www.cpuid.com/softwares/hwmonitor.htmlHit the SETUP • ENGLISH button down on the left.
Opening up the case to see how much dust etc. is in there can also be a tell-tale and giving it a good clean out could resolve if there is a build up.