It sounds like you may suffer from sleep apnea. Sleep apnea occurs when you stop breathing during the night. Most people are not even aware that they do this. If you're married/ have a live in partner you can go to bed early and ask them to watch/ listen to see if you stop breathing at any point. You could also try recording yourself with a camcorder or recorder while you sleep.
If you have no means to monitor your sleep I suggest that you talk to your doctor about having a sleep study done. For a sleep study, you spend the night at a sleep clinic. They will hook you up to wires or electrodes that measure brain waves to see what is causing your problem.
Good luck.