Since around 2 weeks my Macbook Air 2013 sometimes heats up without any reason and runs slowly and sometimes freezes. Right now its running well but is there a reason why this could happen, it did not before and I didn't install anything new...Maybe something wrong with the fan? I once used too much CPU which caused the Mac to crash, this was around the time the problem started...or is this just a coincidence? My internet runs slow too sometimes. Or is it a Malware/Spyware? And is there a way to test if my Battery/Cpu is damaged?