I would definitely run one of those utilities that monitors chip and HD temperature. Everest is the one I use, but there are others.
My laptop did the same for some time, till I got annoyed enough to dismantle it - and found that they'd forgotten to put the "heat path" goo between the chip and the heat sink when they built the machine. Both were pristine and shiny. A quick dob of "Thermpath", and it's been right as rain ever since.
If it's chip overheating, you could try blowing out the vents to clear the dust and fluff. If it's a new laptop, there shouldn't be any - and if it's under guarantee, take it back anyway, because doing the "missing heat path goo" fix will almost certainly invalidate any warranty.
Otherwise, as others have said, look at the logs.