This has happened to me twice, the second time just happened in the middle of the night last night.
Maybe 2 weeks ago, I picked my phone up from my desk to check the time, and it was on the red "droid eye" screen rebooting. Didn't notice any problems after that, so really thought nothing of it.
Then last night, I just happened to wake up in the middle of the night and went to check the time. The screen was black, and couldn't turn it on using the power button or the slider. Had to pull the battery. Worked fine after that, but now this has me worried. I'm actually not too worried about the phone itself, but about what would have happened if i didn't see that the phone was off. My alarm clock wouldn't have gone off, and I would have been in lot of trouble at work.
Could it be a loose battery connection? maybe if the phone gets jarred or shaken the battery comes loose? but the phone was just sitting on my nightstand both times it went dead?
I dunno....