Could have various problems. Firstly, check if the Airflow for the CPU Fan, and the CPU Fan itself is working correctly! For to do that you may need to open up (disassemble) your laptop, be careful with that!
Next would be to check the Memory Modules! Because of moisture, the contact feet's get oxidized and need to be cleaned. For that tkae out the modules and use an soft Pencil Rubber for to clean the contact feet's, not use an hard or even medium Rubber for to not damage the Gold plating of those contact's.
If that didn't helps, check the Battery, may it's on the end of their lifetime?!
Noting? Go to the next Service Center!
Have a nice day.