You have possibly an adrenergic response, perhaps to dreams, but more likely it is due to obstructive, central, or to the dreaded combination called 'complex, sleep apnea. I say more likely because you experience it more often than you would from a troubling dream.

I developed atrial fibrillation near the end of a daily run seven years ago. No idea why, after decades of being fit and running well. Long story short, after many tests, the last one suggested by my cardiologist was an over night sleep lab, called a polysomnography. The result, which blew me away, was 'severe sleep apnea.' When I next saw the cardiologist, he looked up from the report and quipped, 'Well, I guess we know why you developed atrial fibrillation.'