Is it normal to wake up from a nightmare and not be able to move?

Yes it's sleep paralysis and it's normal it happens wen you become lucid in stage4 or "deep sleep" the body won't be able to move but the mind is stuck in a half sleep half waking state.

I'm pretty sure it's called sleep paralysis, which is completely normal, although I've never heard of it lasting for hours.

According to some research it is actually a sleep disorder, and if you've had it once chances are you will have other episodes later on. Usually though people don't have it occur consistently thankfully enough. I've had one myself where I was sleeping with my girl(she's on the right) im laying stomach down head to left and I open my eyes thinking im awake in my bedroom and something, 'someone' tapped me 3 times.....On the left and i freak out and sure enough...cant move a muscle enough to get up. Its a very disconcerting feeling I will tell you lol

I dreamed that a man got on my bed and sat on top of me and held my arms down. My eyes were open and I couldn't move my arms or legs. I was freaked out :o

This is normal. My dad and I have it all the time. I think it may be in genetics. I had a dream that I was going home and it was night, but there was a guard dog. Then I fell to the ground and couldn't move. The dog sat down next to me and I tried to hit it and run away but I couldn't. About 15 minutes later, I stumbled away.....my dad what happens to him is he has waking dream where he can see his bedroom but he can't move. He thinks someone is breaking in and he tries to go and save my brother and I, then he yells at us to run and then we have to wake him up...

It's called sleep paralysis I think, and no, it's not normal. See a specialist.