It sounds like a firmware problem, something to do with waking from sleep, it can't for some reason, I would plug it into the computer (back up the songs if necessary) and rollback to an older firmware and reinstall the newest firmware and see if the problem is fixed.
P.S. When the firmware is rolled back do some testing and load a few songs on it and see if it still crashes, that way if it doesn't you can at least use it on the older firmware...