I used to get this all the time - Sleeping peacefully and hear footsteps coming from upstairs. The footsteps would get a bit louder as they came down a staircase that didn't actually exist in the house. I'd feel like I was wide awake but trying to stay still and pretend I was asleep. A few times, the footsteps came right to my room and I got a glimpse of a young girl as she walked through my room. Other times, the noises were metallic and much heavier sounding. Again, I felt wide awake but could not move even a finger no matter how hard I tried. Rolling over in bed was impossible and it was horrifying with my imagination running wild and in full fight-or-flight mode not being able to move. When I'd eventually wake up for real, it was clear that I was in a super deep sleep and lucid dreaming. I had this experience so often that I eventually learned to recognize subtle clues that I was just dreaming and either wake myself up or change the parameters of the dream on the fly. Now days, the closest I get to this is extremely vivid lucid dreaming where I'm trying to run but can only move in slow motion. It's still spooky but not nearly as terrifying as the sleep paralysis shadow figure thing.