I would like to thank Zon for completing my answer, I wrote about how dreams are basically hallucinations but I guess I was being over-complicated.
It is very possible that it was just a hallucination/dream. However, only you can confirm that…
[spoiler]I am not a big fan of self-promotion, but I guess this calls for my WILD scale. It could help you here Trance Levels With Awareness: A WILD technique. As far as my experience goes, I have not found any scale that is more accurate than that one. (It was based on hypnosis scales and adapted for WILD by myself.)
By checking the second table there you can see that there is a limb discomfort phase which you may wish to move. Then there’s another phase “Catalepsy Ends” in which you may move your limbs involuntarily.
I am just saying that the urge to move is actually very normal there.[/spoiler]
Zon claims that it’s easy to wake up by forcing to move. I have seen some people complain about trying to move during SP and since they realize they are paralyzed, they get more scared.
I really recommend to use the breath trick instead, which is much easier. Breathing is not affected by SP and you can take advantage of it voluntarily.
Just hold your breath for a few seconds (from 8 to 20) then take deep breaths. It has never failed me and usually breaks SP as soon as I take the first deep breath. Because of its reliability I have not needed any other technique yet.