I am a computer repair tech and I agree with everything said so far. Here are my 2-cents:
1. Back up your system.
2. Run a hard drive diagnostics program. If it is a pc you can usually press and hold F8 (or repeatedly tap it) when powering up. On most systems this will open up a screen with several choices. Find and run a complete system diagnostics. If the drive or fan has problems it is best to have it replaced real soon by a reputable tech.
3. If no problem is found then the culprit could be a virus or malware. A program I use quite often is www.malwarebytes.com. Download and run the free version. Do this even if you already have a antivirus program as no program will find everthing.
4. If you still have problems then it is likely that the root programming has been corrupted. Take it to a tech for fixing. (There are free programs that fix roots but they are natorious for deleting too much or not enough.) Generally it takes experience to fix it right. If it is really corrupted it may require a reload of the operating system. (Don't let the tech talk you in to a complete wipe of the hard drive and re-install. This is rarely needed and is often the last resort of a lazy tech who can't find the problem!)
Good luck!