7 22 2:00 am.  So this has been my experience for the past two or three years, and it is what has made me completely loose faith in the possibility of me being horizontal and going to sleep.
I lay down a few minutes ago, thoroughly enjoying the feel of my futon bed, the comfort of the blanket, the general coziness of the setting ----- all this lasts about ten or fifteen minutes.  then a leg gets that crescendo, build up feeling.  and then a spasm.  The simple fact is that my body simply will not allow me to lie down and sleep.  Any unnatural sleep posture is fine.  I often fall asleep sitting, not in some stuffed chair, but in a hard wooden one, or sitting on a barstool.  I fall asleep there and usually fall out.  waking at the moment of impact, cracking my jaw. bloodying my nose, striking hard my skull.
I can fall asleep while pedaling my recumbent trike.  I swerve off the  road (there are sharp drop offs on the hwy to Cayucos) or into the road, or I simply come to a stop and sleep in the middle of the road.  Waking up is always full of surprises.
I fall asleep while friends are talking to me.  I can sleep outside on my chaise lounge if the back is raised up (and get a sunburn)

If you accept the body/soul duality, then I would say that the body has no need for sleep, that it is the soul that craves it. really craves the liberation that dream imagination brings.  Tom Waits keeps coming up lately.  He has a great song, "You're innocent when you dream"