This happens to me as well. I do not suffer from PTSD. But I do suffer from anxiety. I am going to start a journal. As I lay in bed about to fall asleep. I startle awake with the feeling that I wasn't breathing. Then my heart rate goes up. This happenes several times before I finally fall asleep. This happened to me the other night right after I came home from playing soccer. I was having asthma symptoms so I took a breathing treatment. Then had to take xanex for anxiety. Then the sleep jolt/not breathing thing happened (again). I have read that cortisol levels change as we lie down. And it's possible stress can be a factor. My dr. Suggested a sleep center for apnea but because this only happens to me while I'm trying to fall asleep I'm positive it's not that. Sorry you are all going through this. It's very scary. Sometimes I'm scared I won't wake up. But I do everytime! It's got to be stress. Take care.