Hello. I have a question regarding something that I normally experience during the onset of sleeping, right before I fall asleep or during sleep but not limited to just this scenario, as I have had it happen a few times while awake. Last night, while just falling asleep I awoke and immediately jerked my head to the left, in such an extreme fashion that I was afraid that I might break my neck. I've had involuntary jerking movements like this before in my head and neck, as well as in my arms, upper torso and legs but they seem to be rare and do not happen in succession. But when it does, it's involuntary and a little scary. I also have shaking in my hands and sometimes in my neck and head, depending on which way I turn my head or hold my head up. It's not constant but is prevalent. I smoke and have been smoking for 12 years and have had history of some drug abuse and alcohol abuse in my teens. I'm not sure if this might have anything to do with it but am a little concerned. I appreciate any advice and medical opinion and thank you for your time.