Your legs may hurt when you sleep because you are experiencing growing pains. You may also have restless leg syndrome which can cause sore legs.
a stream
Maybe you should sleep on it for a little while. And see how it feels then.
Either on your back or on your side.. if you sleep on your stomach then you can hurt your back.. I learn to put a pillow between my legs when i sleep on my side to prevent me from rolling onto my stomach.
what is asynchronous jerking of legs and head at sleep onset
Yes, it is correct. You could also say "you have pain in your legs" or "your legs hurt".
Does it hurt?
You've probably slept with you legs in an awkward position.
Yes, it will actually dose standing on three legs. But for real REM sleep, they lay down in recumbancy or out on their sides.
Because you move your legs so much and they are not used to the pressure.
Lack of blood to your butt or you hurt it, lets say u fell over and landed on it, then your bone might be bruised and it would hurt to sit on it or sleep on it.
It takes several hours when uneasiness of my legs normlize then go to sleep