So, recently I've experienced 'Sleep Paralysis'. Though it only happened twice, I looked into it.
There are no straight forward answers, everyone on every sight I've read had their own opinions but the link above was what I settled with since it actually had a bit of logic.
Waking up in your nightmare? Probably. I actually didn't know one of my greatest fears would have been being ran over by a train until it felt as if it almost happened..
I couldn't move my body at all. It was as if somebody was putting all their weight on top of me. My eyes were open, and I was conscious. My mouth felt as though it were screwed shut, as I tried to speak, and scream out for my mother. As soon as the feeling ended, I was horrified and my heart was racing. The weird part was what I heard. It sounded so real, it was a train. The sound got louder and louder until the moment where I would expect to get hit, that's when I was able to move.
I must have been sleep deprived to have caused this on myself, but I do recall actually getting my hours the nights before. There isn't much else I could explain about it but I thought I might just share due to my lack of posting and need of sharing.