I knew of a guy with a Seneca 4 that would take off in IMC from an uncontrolled airport, turn on the autopilot, and go to sleep. He didnt have an instrument rating, and used an egg timer to wake himself up. He crashed and killed himself too.
Falling asleep while flying is one of my biggest fears. When your in the middle of nowhere and there isn't anyone talking on the radio and the plane is trimmed really well its easier to do than one would think. When I was between San Angelo and Lubbock I was talking with Ft Worth Center and the only other plane on the radio asked if anyone was there after about 30 minutes of silence. Center responded and said "I've only got 4 planes in my area" the other guy (not the one that called) said "Yeah, some of us are trying to get some sleep here!"