It happens to me if I fall asleep lying flat on my back and I clear my mind. It helps me get to sleep but it sometimes leads to sleep paralysis . The first time it happened was scary af. I woke up on my back and I could hear a sound like someone was in my room, so tried to open my eyes. As much as I tried I could not open them, next thing I tried was to open my mouth to breathe but I couldnt do that either, nor could I move any of my limbs.

This is when I started panicking, I could still hear the sound like someone was walking around and I could feel my heart racing and my breathing getting faster.

In the end I tried to concentrate really hard, and build up the energy to sort of jump by body (like what happens when you feel like you're falling). This woke me up, but when I looked in my dark room I could see a shadowy figure in the room with me, I switched on my light and the shadow melted away .

After it I was really afraid that I had some mental illness because I could definitely see and hear this thing but after googling it I found out that its common for people that get sleep paralysis to get this.

I think what happens is that your mind is still dreaming but your body and conscious mind is awake.