As background, sleep paralysis occurs to prevent body motions in the context of a dream: Having our legs churn while we're dreaming of running would be not so good.

In general, sleep paralysis can be 'cured' by wiggling an extremity. Trying to move the large muscles will almost never succeed, but wiggling toes, the nose, blinking an eye are all worth trying. Almost always, these small motions help trigger the body to realize it's no longer sleeping and should do the biochemistry to stop paralyzing the large muscles.