I'm no expert on sleep paralysis, but I'd think that it's similar to one waking up from a dream and SP not having worn off yet. If these are isolated incidents, then it's probably not a big deal. It could happen. I wouldn't worry about it unless it happens more regularly.

Look up REM Atonia (the scientific term for what has come to be known as sleep paralysis among lucid dream enthusiasts) or REM Behavior Disorder. The latter is where SP doesn't set in, and people act out their dreams. It's not exactly the same as sleep walking, so don't confuse it with that.