Sounds like you have a thermal management problem in this laptop. This could be the result of clogged fans and air chambers. I suggest that you blow out any dirt buildup using a can of compressed air. In order laptops, this can also be the result of the Thermal Interface Material (TIM, a.k.a. heatsink paste) drying out. Addressing this is something that will likely require the services of a technician who is familiar with such activities.
Hope this helps,
...S
