While waking up-if you selected during sleep youre still very confused about what sp is. sp is, essentially, the paralysis of your body while youre awake. rem atonia is when it happens while youre asleep, during your rem sleep periods.sp occurs most often while waking up. many people mistakenly think that sp is most common while falling asleep because some lucid dreamers attempt to induce sp in order to wild. however, this is incorrect. sleep paralysis is naturally most common upon awakening, postdormitally.