Why does my old Toshiba Equium keep switching itself off

[555colm]

Computer keeps switching off

 

[toshibitsu]

The 2 main causes are:

1. over heating
2. power supply failing

Could still possibly be something else, but we'd need a bit more detail on what exactly is happening. Does it just shut off shortly after powering on? Or does it do this at a certain point/while you try to load something? Do you hear any 'odd sounds/beeps' before it shuts down? Does something ever display on the screen before it shuts down(how far does it get)?