It’s not a pleasant job, but your computer (either laptop or desktop) needs to have the dust blown out of its interior once a year or so. The cleanest method is to take it into the garage and either use canned air or the exhaust from a shop vac. Blast the dirt loose, and make sure you get into the crevices and slots. Your CPU is covered with a heat sink with many fins, they need the air to circulate. It won’t usually be necessary to disassemble your laptop, but make sure you put a strong blast of air through its ventilation slots.