The past couple of days, my computer has started this annoying habit of randomly restarting itself. First time it happened was Friday morning, it restarted itself 3 times in about an hour, before running fine for the rest of the day. Same thing happened this morning, and has just happened again twice in the past hour. Along with this, It will occasionally just freeze up rather than restarting, and my internet browser (Firefox) will sometimes randomly close as well. Now, all of this sounds like a Virus, but I've run the virus scanner a couple of times and it hasn't found anything, so I'm out of ideas. Anyone got any ideas/ had any similar experiences?