This has happened to me twice: I press the power button on my Mac Book Pro, choose sleep, close it, unplug everything, confirm that is off (by pressing my ear to it) and put it in my bag. Some minutes later, the laptop wakes up by itself.
Both times I caught it in time. The second time it was so hot I couldn't touch some parts -- it refused to actually wake up, and the screen was blank. Restarting it worked though.
Any ideas what might be going on and/or how to prevent this?
More details: It's a Mac Book Pro unibody 15" from 2009.