it may be that the fan intake, and/or some of the internal spaces is/are blocked with fluff - it's a common laptop problem.
Buy a can of compressed air from any good computer shop. With the machine off, remove any access panels on the underside of the case. Then give the spaces a decent blast from the aerosol spray, paying attention to the fan intake and exhaust grilles.
If that doesn't work, we'll think again - come back to your thread and let us know.