Abrupt Awakenings in the night usually indicate central sleep apnea. You may wake suddenly with a shortness of breath. The cause of this is your brain telling you to wake up and breathe.
When you stop breathing frequently and regularly, carbon dioxide builds up in the bloodstream. At that point, chemoreceptors in the blood stream note the high carbon dioxide levels and the brain is signaled to wake the person sleeping and breathe in air.
When you wake upon not breathing air for a certain period your body is trying to get your breathing back on track and your body is in fight mode….the result is that you wake up breathing heavy to return your blood oxygen levels and respiratory system back to its normal state.