Exhausted, you finally settle into bed, drifting off when suddenly your body feels like it’s “falling,” and you jolt awake. This sudden, involuntary movement, known as a hypnic jerk, can be startling. You might find yourself wondering why it happens, and you’re not alone—up to 70% of people experience this. Despite its common occurrence, it never feels any less abrupt. While the exact cause remains uncertain, one theory suggests that hypnic jerks occur due to the nervous system’s transition as the body relaxes into sleep. Another theory links it to the natural downshifting of the nervous system during the sleep cycle.