Yeah, I've had it a few times. I've not really panicked from it, but it's certainly alarmed me.
The first time it happened I think was a couple of years ago. I randomly woke up to some tall, strange figure dressed completely in black (couldn't see their face), and leaning over me about to stab me. My initial reaction was to jump out of bed, but I couldn't move and as the figure got closer I flailed wildly and jumped out of bed just to watch them disappear as I lunged for them. I sat back and was very confused. I fell asleep shortly after and it almost feels like a dream now.
The last time it happened was about a month ago when I was trying to sort my sleep out (for the billionth time), so I was suffering from extreme sleep deprivation. I had no images this time, but it happened about three times on the trot where I woke up extremely hot, confused and unable to move. Oddly, I did find breathing quite difficult but it passed after a few seconds. As it sends you into 'fight or flight' I was almost scared to go back to sleep in case it happened again. I sat up for about ten minutes listening to music to calm down, put my lamp on and just fell asleep. Each time it happened that night, it was a precursor or following on from a lucid dream (which were more like nightmares anyway).