My framerate has been dropping while playing MGSV

It only started doing this a few days ago, so I stopped playing as much, but when I play it still does it. Nothing onscreen seems to trigger it, it just happens once in a while, and only for a few seconds then goes back to normal. The game itself doesn't slow down, just the framerate drops a bit. I also haven't noticed it doing it during other games.

Does this mean that my system is dying? It's one of the old fat ones. 80 GB hard drive, 2 USB slots, no chrome. I'm not sure of the exact model.