If this has happend before you could link it to
Sleep apnea. Accourding to "Exploring Psychology In Modules Seventh Edition"
"Sleep apnea aslo puts millions fo people at increased risk of traffic accidents. Although 1 in 20 o fus has this disorder, it was unknown before modern sleep research. Apnea means "with no breath," and people with this condition intermittently stop breathing during sleep. After an airless minute or so, dereased blood oxygen arouses them and they wake up enough to snort in the air for a few seconds, in a process that repeats hundreds of times each night, depriving them of slow-wave sleep. Apart form complaints fo sleepiness and irritablility during the day-and their disorder.(The next morning they have no recall of these episodes)
Sleep apnea assoiacted with obesity, and as number of obese people in teh United States has increased, so has this disorder, particularly amoung overweight men. Anyone who snores at night, feels tired during the day, and possibly has high blood pressure as well should be cheacked for apnea...."
I'm no expert, but this might be happening because when you enter this low-wave, relaxed state, and maintain it with out going into R.E.M., this dissorder may be what is happening. Like I said, though, I'm no expert and have no right to advise anyone.