If it truly is freezing randomly and you can't spot any patterns of "oh it normally freezes when I'm running X" then it's almost impossible to diagnose even when sitting in front of the computer.
You can try running a full scan with both your anti-virus and malware bytes, run a full check disk, upgrade all the systems drivers to the latest versions, make sure you are running the latest versions of any software you have installed and also make sure all windows updates are installed... (all of which should be done regularly anyhow and if the "local guy" if worth his salt he would have done all the above as a matter of course.)
But to be honest, with genuine random freezes the easiest option is normally to backup all your personal data and then run a system recovery back to factory state and then reinstall all the software you use and copy the backup of your personal data back onto the system.
At two years old giving it a restore back to factory settings is worth doing even if it wasn't freezing as it will get rid of loads of crud you don't need and make the whole system run better and faster anyhow