The full body shudder, right at the moment of falling asleep, is fairly common in TBI patients. You may find that this symptom dissipates as your recovery progresses.

Mark from Idaho might know if there are any medications that can dampen this down. I opted to just live with it. While it's annoying, there is no evidence that it's harmful. Believe it or not, one can learn to live with it.

My exaggerated startle response on the other hand... sigh