When you sleep and dream, your body is supposed to shut down all motor skills... so you don't run around and punch shit like you would in a dream. Now there are different levels over "shutdown," one of which is where people get panic attacks because they're brain "shuts down" too much... not that it REALLY does, but its a perception where your body is no longer working, and you either panic, or just jolt your body awake (i jolt, a LOT, when i try and fall asleep. Hell, just happened last night.)
Now, when its time to wake up, sometimes your body isn't as quick as your mind is to get up... which is where the paralysis feeling comes in. You're still in a dream state, you very slightly take in your surroundings, but things aren't right. I've had this happen many times as well. So in reality, you were still dreaming, but your mind was confused because it was trying to take in reality... but it wasn't quite time.
Its a really scary feeling, but really, its just dreaming.
The body does WEIRD things sometimes.
Hope that was half understandable. lol