Whenever i lie down i have these constant sometimes intense muscle movements: mouth, jaw, lower abdomen, and legs. what causes this?

That's a poser: Depends on how long you've had it. If it came on before the age of 25, it's idiopathic or familial. If it's recent e.g. 3 months, I don't know. I must confess I've never heard of positional nonkinesigenic dyskinesias if that's what your movements are; can't quite tell from your post. If it's recent you should see your doctor. Could be a basal ganglia lesion of some kind (speculating only here).