I've only ever had this on a train. We were going up north, and I was having a series of the most lucid dreams of my life. On the final evening of the trip, I became fully aware of my dreaming while still asleep, and felt as though my "awake self" woke up in my own mind. My eyes were closed, and it felt as though I was standing in a spotlight, amidst pitch black. It literally felt as though I was standing within my own mental confines. I frequently become aware of my dreams, but in this case as hard as I tried to do a tried and true "spasm" to wake myself up, I realized that I had no control of my body. So, I stood there, in my own mind, I frantically try and think of a way out. After minutes of focus, I pulled myself out of the dream, only to jerk up and fall right back down, into the "abyss". I stayed there for a few more minutes until I finally got myself up again, this time remembering to flip on all fours and shake my head to fully wake myself. I didn't get back to sleep until about a day and a half later.
There were no shadow people. but the mere mention of them has been literally sending multiple shivers down my spine for an hour now. I'm currently waiting on the sun to come up to try and get to sleep.
All of this makes me miss when a horror movie used to do the trick.