I do respond to the "myoclonic jerk" while falling asleep at night and wake to a horrible adrenaline rush and pounding, fast and usually irregular heartbeat as I drift off to sleep. I notice more that in the past when I would take naps, and even now when I go back to sleep in the mornings after my husband leaves for work (I'm on vacation for the summer :), if I wake suddenly my heart beats super hard and fast. It happened yesterday morning and I went back to lay down and my covers were moving my heart was pounding so hard. I was also very nauseous which makes me think maybe it was blood pressure issues...like orthostatic hypotension or something. With naps and going back to sleep for me, I think I sleep harder which makes me feel really crummy if I wake up suddenly. If I wake suddenly I usually jump up.
I don't know if this is like what you're feeling, as it sounds like yours is happening as you try to go to sleep, but it seems my skippy heart gives me more trouble when I'm asleep than when I'm awake (or it's just more frightening when I wake to it).
I also get that feeling like my heart is racing but as I feel my pulse, it's usually slow and steady. Maybe adrenaline?? I feel this a lot during the day. Sometimes it makes me short of breath...unnerving feeling for sure.
My wife gets this too.
If she has a daytime catnap for a few minutes, her heart is all over the place afterwards, thumpy and irregular. So much so, she hates falling asleep in the day, but the beta blockers make her tired.... She can't help it.
Happens even if she's dozed off for only 5 to 10 mins.
I HAVE THIS TOO. I'M A FEMALE 62 YEARS YOUNG AND HAVE ALWAYS HAD THIS. AFTER A SHORT CAT NAP, I WAKE UP AND MY HEART IS POUNDING FOR ABOUT 3 MIN. I FEEL FINE, JUST A VERY FAST HEART RATE. DOCTOR CANNOT EXPLAIN.