My friend and I have been hving these weird experiences and i dont know what they are or what theyre called.

I would be falling asleep, Really confortable, and then ide be sorta dreaming but its way too faded to see anything. I'd be in both bodies, my dream body and real one and then something in the dream would come out of no where and hit me.
i would be Jolted awake and my muscles would tense up really fast and ide twitch wherever the thing hit me.

Like say, a rock would hit me on the leg, I would be woken up from that half sleep state so suddenly and my muscle would hurt and ache really bad.

This has happened with a number of items too. I would get hit by cars and my whole body would tense up really fast and it would hurt! i fell off a cliff and landed hard on my back, too! that one was really trippy because i also had that feeling of falling as i was jarred awake.

What is this and is it normal? Or even bad for me?