Last time it happened to me was about a year ago.
I didn't know there was a name for it, but stumbled upon it on the internetz around that time.
Has happened off & on since I was a kid but hasn't happened in a while.
Often times it feels like you're half asleep and unsure if you're dreaming or not, and you can't move at all. Sometimes it's accompanied by the feeling of a "presence" in the room, either audibly, visually, or sometimes you "feel" it through touch. Like someone or something is in your room or in your bed. You may feel it touch you and sometimes you won't.
But to the people that are "frightened" by it - it's perfectly normal and harmless. Most people will experience it at some point. It has something to do with the brain still sending signals to the body that it's still "asleep" even if your eyes are open, and takes a moment for everything to normalize.