I have the same thing happen to me maybe a couple of times a year. I do not think I am going to die, but I am quite scared and disturbed by the sensation.
I have researched the disorder myself on the Internet and I am 95% sure that it is related to, or IS, Sleep Paralysis.
I say this because when it happens I am sure that I am conscious, awake, and not dreaming. The rushing, buzzing, kind of noisy-inside- sensation starts to come on and I get scared, and THINK that I am stopping myself from falling sleep or whatever is going to happen if I let the buzzing sensations just happen and continue.
It's like something bad is going to happen if I allow myself to let the buzzing sensation build.
What I believe would happen is I would either wake up - because I am actually asleep and dreaming, or in some weird sleep/waking state of consciousness - or I don't know what. But the feeling of dread never allows me to just go with the flow, as it were.
I hope this helps others and that I have explained myself good enough. This is just my own opinion of what is happening. But like I said, I am almost positive that it is something similar to, maybe even something building up to - Sleep paralysis.
I believe that the sensations are some kind of auditory/sensory hallucinations as a result of not actually being awake properly like I assume I am.