After my sleep study with nasal cpap I went over a week with no vibrations. I believe mine is related to injury to phrenic nerve. I searched internal vibrations 2 years ago and injury to phrenic nerve was one reason, and the injury can be caused by swallowing large gulp of air, which I did taking meds, sneezing or coughing very hard. It sorta makes sense to me since the phrenic nerve controls the diaphragm and the diaphragm controls the breathing and air forced in through cpap does something, I'm not sure. All I do know is when they wake me up, I can place my hand on my side and actually feel the vibrations inside. I slept with a stethoscope under pillow so when I had them I could see if that would pick anything up. All I could hear was a very low humming sound. Mine are in my torso area and will move down to pelvic area and every now and then I can feel them in my butt cheeks. It is so crazy. I'd be willing to participate in a study if there were doctors who were willing to get to bottom of this. It is so puzzling.