It's true that your body goes into sleep paralysis when you are dreaming, to keep you from acting out your dreams...but I can't see how this would cause anyone to hyperventilate. Are you an anxious person? Do you have any anxiety? I've woken up once and started hyperventilating because of a panic attack. But other than that, I can't see any reason why you would experience this. Maybe someone else has experienced something similar?

Also...has anything changed recently in your life. Are you taking any medications? etc...