It sounds like he might just be hungry. I wouldn't worry too much about it. I would worry more about your temperature gauge being inaccurate. Are you using a dial or strip? A digital indoor/outdoor thermometer is more accurate and a relative inexpensive solution. (wal-mart's brand is accurite)

I find that when I go into my snake room, that there's usually at least one out and roaming in their cage. Nothing to worry about.