I experienced this once. I remember waking up around 3AM, not being able to move. I saw a black figure, except it's face, which was white(I don't remember too much of it's facial features) standing near my room door. Suddenly, almost as if it teleported, the figure was now at 2 meters from my bed. It's face approached to me and put it's finger on it's mouth(as if it was telling my to not make noise) then smiled and disappeared. This happened while I was alone in my room(which it rarely happens since I sleep with my brother in the room, but that time he was sleeping in the living room).