My arms dream before the rest of my body.

So I've had this experience a few times and its always weird.

sometimes my arms will start dreaming while the rest of my body dont and when I try moving my arms, it will feel perfectly normal as if they are moving, but they are actually paralyzed in bed already while the rest of my body can move.
today I had a false poistive reality check because of that. I tried closing my nose and breathing through it and it worked, I was really confused because It didn't feel like a dream at all (and it wasnt, kinda) but my arm was dreaming that it had closed my nose so the reality check gave a false positive.

Wonder if that had happened to anybody else?

I'm not sure what you mean by your arms dreaming but, I'm going to take a jab at it anyways.

It could BE a number of things for you:
1. It could be that you are having some hypnagogic Transitioning sensations that were more physical in a WILD and when you did an RC but, it failed you. Then you were left confused? Does this sound about right? An RC will not work 100% of the time.
It's different for everyone.

2. It could be that you had some hypnagogia that can also happen when you are sleep-deprived?? And you are about to enter REM and Deep sleep. I think? This means you may not get enough sleep and a lucid dream maybe on likely. I don't know your sleep pattern so I don't know what is going on for sure. Did you experience it early right when you went to bed for the night? How many times have you have had this? Or did you do a Wake Back To Bed?
You know that you can have hypnopompic hallucinations at the end of a dream too.
3. If you are on med it also can cause hypnagogia like that.

With me: Once in a while when I have a WILD (Wake Initiated Lucid Dream) I could feel the sensation of an earthquake only around my feet or around my hands along with some strange imagery and some strange sounds.