Yes! This is exactly what I've been experiencing too! I keep reading all this postural connection but never found anything on it happening upon lying down. I don't get it on standing or exercise hardly ever. I get it at random times , too, but 75% of the times I lie down I get it. Just finished 2wks on heart monitor so hopefully ill have results in a wk. Feels so stimulating heart being so weird, that even when I "know" I'm ok, it's still hard to sleep. Sorry you are going through that, but have to say I'my relieved to find somebody else with this. Please post anything else you find out. I've also had blood pressure drops upon lying down. Do you get those too? I believe my dysautonomia is from car accident 7 wks ago. But dr doesnt. She's puzzled. Heart started after couple wks & blood pressure drops about 4the wk. Not sure if it would be from my concussion or whiplash. Do you know what yours is from?