macbook pro keeps shutting down and restarting randomly
My macbook pro often shuts itself down and restarts itself when it's on but I'm not working on it. It particularly happens when it's just on playing music from either iTunes or Spotify but can also happen if I have a webpage up but am not actively doing anything. Does anyone know why it does this and how I can stop it?
Thanks
MacBook Pro, Mac OS X (10.6.8)