Trouble with startup of laptop

My laptop, a Toshiba Satellite, has a problem where when the power button is pressed it will start for about 2 seconds and then shuts down. It then loops where the machine acts like it is starting only to shut down. Any idea where I can look for the problem.
 
I had this issue with anPavillion DV6000 and the problem was the NVidia graphic card. I had to buy a new motherboard...which I didnt eventually, and got a new laptop.
 
Back