Weird. I have a dell workstation that does the same thing, except the first time all the fans rev up to full speed before abruptly shutting off. Then the second, it shuts off really quick. Then the third, it works flawlessly. I think it happens more often when the comptuer is unplugged/disconnected from power quickly. So maybe it's something to do with shutting down? That's a wild guess based on my problem that I definitely don't care enough to troubleshoot.