I get random frights when i'm either asleep or trying to fall asleep. like i will be laying doing nothing and get startled where my heart skips a beat (not literally) and my body jerks suddenly. i work night shift. weigh 105kg. 1,79m tall.

Jerks: Infrequent Myoclonal jerks or a startle like reaction can occur during the half awake, half asleep phase and may not be due to any serious neurological disorder and are rarely harmful. I assume you don't have any other neurological symptoms. Muscle fatigue may play a role,however. I don't think there's any relation to your body build. If you still have concerns, consult a neurologist for evaluatio