Hi, avatar. I'm sorry you are having a hard time. I know a little bit about this type of thing from experience. First of all, I guarantee you that this is common and this BY ITS SELF is NOT a sign of mental illness. And for people who so ardently attempt to make contact with other dimensions, it strikes me as a little odd to jump right to "Dude you're mental".... anyway... 

The fact that this is happening to you while falling asleep suggest that you may be experiencing very common out of body / lucid dreaming phenomenon.

Often when people start to leave their  body/ or become slightly out of phase, they experience a strong "vibration" sensation along with hearing loud ripping or buzzing sounds. Sounds like what you are describing. Often In this state you will here people calling your name or saying things to you along with paralysis. Some people will experiences something sitting on them/ some times harassing them. Google "old Hag". It's been my experience that the voices are just left over mental activity you become more aware of in this state. Our minds are always primed to hear someone say our name and our mind will jump the gun. Anyone ever feel their cell vibrate in their pocket when it didn't?

When I was younger, I would sometimes be startled by a voice calling my name while drifting off... in my mothers voice. Once again very common.

The first time I induced an out of body experience, I relaxed very very deeply using breath control. Soon my body was completely numb and vibrations spread throughout my body. As I focused on them they became more and more intense. Soon it felt like I was being electrocuted and there was a loud rushing sound. Then there was a thunder clap and I was 3 feet above my body flailing wildly. When I snapped back I was scared shitless. I looked it up online and it turns out to very common.

So the good news is you are not alone... and probably not crazy... and probably not being harassed by an entity. And may have an opportunity here to develop the ability to leave your body.

The bad news is, it might be an entity. There is a lot of stuff out there in the etheric and astral + hyperspace. Thought forms, spirits, elementals etc.

And IF you are being harassed what you need to know is these things can't *hurt* you like you can be hurt here. In those realms they use and feed on emotion. Some of these things will try and scare you. But that's all they got.

Let’s put it this way. Let’s assume that spirits and demons and elves exist all of it. What is a ghost going to do to you? It is a very limited being. Humans however, while being very ignorant of ourselves, possess many, many dimensional bodies. That is what allows us to travel from the physical to the etheric to the astral to the mental  and throughout hyperspace. We show up in their back yards like big dummies, without even knowing how we did it, while most "gods" could never manifest on a plane other than their own. Why would a demon make a pact with a human? Because we are much much more capable then we know. And they would like to use our power.

Point being If you face almost any of these things without fear they run for the hills.

Now this is just what I think. If this is an area you don’t want to go, a doctor could prescribe you something that will numb your senses and lower your awareness. Then you won’t be able to see it. So out of sight out of mind right? Right?

Naw, you are crazy.    (read Robert Monroe’s journeys out of body)