Toshiba laptop that shuts off 5 min after booting...

Question

i have a tosiba a25 satillite laptop, each time i start it up it runs for about 5 min. during that 5 min i can feel heat comming off the key board and then it just shuts down. it will reboot after a short wait. i checked the fans they are working fine. any suggestions of diagnosis or a repair suggetion would be greatly appreciated