When I enter SP, i get the same results as you, "frozen" you try to move and scream but you just cant move and you freak out. What I do is when i enter SP which is scary for me everytime, I calm myself down and say that its just a dream. Sleep paralysis is already a dream, when I go into SP and cant move, what I do is rolling out of the bed then you can suddenly pop out and move again. For me sleep paraylsis is already a lucid dream once you can move.