How old is that satellite laptop?
Certain satellite laptops with Mobile Pentium 4 Prescott CPUs were notorious for overheating (and shutting themselves off as a result).
If it's still under warranty (highly unlikely), call Toshiba.
If it's not...then try cleaning out the vent holes with canned air. You may have to go as far as removing and reseating the heat sink (using new thermal paste, of course). Even then, the P4 Satellites will still give you grief.
Otherwise, try one of those laptop cooling pads and NEVER remove the laptop from it...