I'd be inclined to believe thermal problems here, you can download CoreTemp http
/www.alcpu.com/CoreTemp/ to check your temps. I'd also be inclined to believe that the laptop is in dire need of a thorough physical cleaning. The bad part of that is disassembly is required, the good news is there are a few videos that show how and can be of help like these
https/www.youtube.com/watch?v=STc5BlRSK5o and
https/www.youtube.com/watch?v=UhxiBaF2cdw
If it seems too overwhelming of a task, you can take it to a local PC shop for service and cleaning but I will recommend it be done.
While that is not the only possibility, it is the most common issue