Numbing body parts...

[SikWilly]

Funny thing happened last night...  As my body began to fall asleep, I had the sensation of everything slowly numbing.  As my face began to numb, my lips did to.  This gave me the sensation that my mouth was slowly opening because the upper lip could no longer feel the lower lip!  Ha, ha!  I had to strongly fight the urge not to bring feeling back to make sure this wasn't happening!  Ha, ha.  Anyways, I got through it without waking my face up.....

[Xanth]

You were consciously observing your body falling asleep.