I think your problem is that: there is dust in the fan assembly, and/or your thermal paste is cooked and your laptop is overheating. You can dissasemble your laptop and check for any dust that might have accumulated in there and change thermal paste if it is completly hardened. Make sure you seperate the fan and heatsink as most dust is hidden in there.
Please note that I am not responsible if you some how break your laptop while dissasembling it. There are probably some dissasembling tutorials on YouTube so take a look at them and be careful to disconnect the battery before doing anything.