Random resource hogging

So I'm using my computer one day, just doing my normal computer stuff, then all of a sudden. WHAM! My computer is hit by a brick wall. All of a sudden my processor, GPU, and HDD are all maxed out with a 99-100% load. It gets so bad that my comp auto downgrades to windows basic scheme because so much resources are being utilized. I can barely use my comp because it's lagging so terribly. And then when I least expect it, it leaves, just as fast it came. My comp reverts back to it's aero scheme and everything just continues normally.

Does this happen to anyone else? Can someone please explain what is happening to my computer?

Thanks in advance