My toshiba laptop keeps shutting off after 5 minutes of being on, what can i do?

I have a Toshiba Satellite laptop that's a little over a year old that keeps shutting off. I've had it a little over a year and had no problems until about a month ago it started shutting off periodically, now its every time its been on for 5 minutes. It's acting like its overheated, but its not even warm.