I had that experience once, in the house I'm currently in. I had all those symptoms. I think it's a misfiring in the brain where you're semi-conscious but still dreaming and the mechanism for paralysis while sleeping is still active, hence you feeling unable to move. If we didn't have that mechanism, sleeping would be a lot more dangerous.
I'm not sure what causes it, but it's an interesting phenomenon. It sucks while you're having it, that's for sure. That feeling of something malevolent right there with ill-intent toward you is staggering, nightmare/dream or not.