Science on Instagram: "Ever felt a sudden jolt or twitch just as you were drifting off to sleep? This strange phenomenon is known as a hypnic jerk or sleep start. It's a completely normal involuntary muscle spasm that occurs as your body transitions from wakefulness to sleep. Scientists believe it may be triggered by stress, caffeine, fatigue, or even the sensation of falling. In this video, we break down the science behind these unexpected twitches and explain why they happen — and why there's