Past 2 nights, drifting to sleep then my body physically jolts. why? no nightmare, no anxiety.

Sleep jerks: This phenomenon is well known. It is called "sleep myoclonus". Involuntary strong large muscle contractions occur spontaneously and only occasionally during sleep. It generally causes no problem for the person who has them. It may cause a problem (bruises) in the partner who sleeps with a person who has myoclonic jerks.

Good question: The brain controls the body and its movements. When the brain is ready for sleep it cause us to fall asleep. The body moving is a sign that the best position may not have occurred. Sometimes these movements are called myoclonus, but do not indicate a disesase. Try to avoid electronics before bed and no tv in bed.

Sleep disruption: Often people will be woken up by dreams but not remember content, that doesn't mean it wasn't a dream. I teach my No More Nightmares class with thePlanned Dream Intervention skill that teaches the sleeping brain there is no such thing as a bad dream, so you sleep through your dreams and don't have the movement. Please see the No More Nightmares book and training.