When did this symptom started to appear or happen?
How old is this laptop?
Does your laptop get just as hot while in safe mode? If you haven't try this please do try. Restart your computer and go into safe mode, and stay logged in safe mode for 30 minutes running simple task like word and so on.
To log into safe mode you will need advanced boot options menu Advanced Boot Options
My initial guess after reading what you describe seems to be that it could possibly be heating issue inside(fans being slowed down due to dust), a lot of dust and so on. Another possibility could be a virus, also would you please update your system specs. It would help, System Info - See Your System Specs