That's called sleep paralysis. You are lucky, you can do it again.Once I found myself completely unable to move while lying on bed. I tried as hard as I could but I couldn't get up or move my limbs or even my head. And that was the "uncreepy" bit. There was also a doll like figure standing next to my bed and it was watching me. Eventually I was able to get up in a burst of determination. I then grabbed the thing (whatever it was) and tossed it out from the balcony.
I was sweating like hell after the ordeal so I went to take a drink of water and left the almost empty glass of water in the center of the dinner table, and then went back to bed. When I woke up in the morning, the glass was on the table. Did I just dream up the whole thing except the sip of water? Because I don't remember going to take a sip of water in the night just like that, I distinctively remember taking it after the ordeal and that's why I placed it on the center of the table so I would be able to tell it wasn't a dream. But was it? I honestly don't know.