Why do I get stiff and unable to move at night when I wake up suddenly?

Last night for example, I woke up several times and I was so stiff and unable to move my neck from one side to the other, I wanted to, but I just couldn't. Sort of like being half awake and half still in a day dream, but I panicked and still couldn't move for about 10 seconds and the worst part is once I realised, I focused on my breathing but I couldn't seem to do that either. Obviously that doesn't last too long, but the panic and the thought of it is terrifying and I'm having difficulty WANTING to go to bed now.
It's very confusing to explain, but if you know what fainting feels like and when you're waking up from that but you can't yet move your limbs or if you are you're not aware that you can, and you feel like you're not breathing even though you are.

I don't know at all, and frankly, I'm a little scared.

To tell you about me I'm a fit female, 20 years old, a bit low on iron, but i'm working on that, and I eat fairly healthily. I put more good than bad into my body, anyway.
Asked Feb 17, 2015

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