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.
Maybe you should sleep on it for a little while. And see how it feels then.
a stream
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
Not entirely, no. It'd be better to say "there's a pain in my legs". To say "my legs are painful", is to say "my legs can hurt people", pretty much.
Does it hurt?
You've probably slept with you legs in an awkward position.
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
Sleep
lay down and alleviate your legs