Automatic shutdown over heating

Hi, The processor cooling fan it might be loose or the fans and heat sink is very dirty. At the rear of the computer remove two screws that secure the side cover and remove the side cover.Check the fans four locking pins if they are loose. Clean the cooling fan and the heat sink and put little fresh thermal compound in the inner part that touch the processor surface. Get back to us if this information help you solve the problem.

Turn the computer off.
Remove the side-panel, to expose the motherboard.
Turn the computer on.
When you see PRESS <blah> TO ENTER BIOS SETUP, press the <blah> key.
Use the "arrow" keys to move around the BIOS SETUP menu,
looking for any "system health" menu-entry.
Press the "enter" key to select that menu-entry.
It should report the current motherboard temperature, and the current CPU temperature,
and the temperature-limit, beyond which the motherboard will force a shutdown.
It may also report the speed of the power-supply fan, the case fan (if installed), and the CPU fan.
Also, take a look at the fans, to confirm that they are spinning.
Replace any non-functioning fans.