Sleep Paralysis
Sleep paralysis is a phenomenon where you wake between a waking and REM state and cannot move. The body is deliberately paralysed during REM sleep — this is normal and protective.
Many experience hallucinatory sensations — figures in the room, pressure on the chest, voices. This sounds frightening but is harmless. Knowing this removes much of the fear.
For lucid dreamers sleep paralysis is an entry opportunity: with practice the state can be redirected into a lucid dream (WILD technique). Stay calm, breathe, and mentally imagine a dream scene.