Been there, done that. Still do it, actually, and it's not limited to when I'm in bed. Often when I'm at the puter, Wonton hops up on my lap to go to sleep. Thing is my left arm has to be in a certain position, cos he snuggles his head into the crook of my elbow. I can type, but thats it - my right arm/hand is free but my left is trapped in one position-the position that supports Wonton's head, and lets me type. So it always falls asleep eventually...and I wait til the last possible minute before I move it, cos I don't want to disturb him.
And yes, at night he snuggles up to me, and sometimes I'm stuck in a certain position, cos moving would mean jostling him..and he just looks so peaceful, sleeping there either curled up in a little ball, or all stretched out next to me..I just don't have the heart to disturb him..so I don't move. The things I do for that cat :p Sometimes though, I do move..and he always gets up and gives me the dirtiest look imaginable