Heart races while about to take a nap?

I’m a 14 year old girl and I was just trying to take a nap and I was still awake while I was dreaming almost like lucid dreaming so then in my dream I start to float above the ceiling and when I do it’s just black and my heart races fast and when I try to wake up I’m stuck in this limbo between waking up or going back to bed and my heart is still racing but when I actually wake up I feel my chest and my heart is normal. I was in this limbo a few times before actually waking up. I don’t know if it was just in my dream or real life but I got a bit spooked.