Why do you shiver when falling asleep?

Shivering when falling asleep is often due to a drop in body temperature as the body relaxes and transitions into sleep. This response can be linked to thermoregulation, where the body may involuntarily contract muscles to generate heat. Additionally, it can be triggered by a sudden release of tension or relaxation after a long day, leading to temporary muscle contractions. In some cases, it might also be related to the body's natural sleep cycle or even vivid dreams.