Well as a test I left it in my car overnight (in my underground garage). It wouldn't boot in the morning, which further confirms that it does have something to do with temperature. I let the drive run a little, and then I pulled it out and back in and all was fine. So the drives I think when cold do not spin properly, they need a warmup. Which explains why leaving it in standby all night is a sure winner.

warsaw, Are you running Hijack? Do you mean you are rebooting through Hijack?