|Could be all manner of things. Run MalwareBytes on it for starters to see if it gives it a clean bill of health:|
Use green icon top right. Let it fix all it finds and unless it is clean paste the log on here so that we can take a peek at it.
Another possibility is overheating. You haven't given your computer make and model number so we don't know if it's a PC or laptop. For a PC clean the vents, fans and CPU heat sink - also, if it has one, Display card heat sink. Not so easy for a laptop but at least clean the vents and anything else you can access.
Always pop back and let us know the outcome - thanks
message edited by Derek