Just as I begin to fall asleep, I either feel like I am going to pass out, or I feel like my heart and lungs are not working. This sensation occurs just as I am falling asleep, so I force myself to wake-up. This cycle of feeling like death is near, and forcing myself to wake-up, usually robs me of 2 to 3 hours of sleep. It does not happen every night, but when it does happen, I feel afraid of falling asleep because I am sure I am going to die. I have done plenty of research and I know these symptoms are imaginary, but knowing that fact does not help. Why is this happening? I have no stress in my life. Why is this happening?