Understanding why hypnic jerks happen requires a closer look at the stages of sleep:
Stage One: Light Sleep Onset
This is the first few minutes after you begin to nod off. Your heartbeat slows, your breathing becomes more even, and your muscles start to relax, though occasional twitches may occur. Brainwave activity shifts from active wakefulness toward slower patterns, setting the stage for deeper sleep.
Stage Two: Preparing for Deep Sleep
