I've had this too as-well. The only thing I could think of after many visits to doctors and tests is that it was either central nervous system (CNS) related or some sort of inflammation in or around my heart that got aggravated with positional changes or pressure when l laid down.
For the CNS issue, I suspected that maybe when signals were sent to my heart to speed up or slow down it aggravated the cells in my heart that were causing the PVCs.
If there is some inflammation in or around your heart it can be caused by various benign things. One that I suspected for me was a viral infection, probably a Coxsackie viral strain which can get to heart tissue. As I had kids in day care at the time the risk of this type of issue for me was higher. When mine started I was in the middle of a GI infection.
Remember that only heart cells can cause PVCs or any other type of ectopic beats. For the great majority of *benign* ectopics the cause is something called "enhanced automaticity" (EA). When you've got some cells with EA going on other outside factors such as pressure, nerve stim, hormones, adrenaline, certain medicines, certain foods, can further aggravate the EA and make them wig out.
Have you ever had a twitchy muscle? similar, but in your heart.
Mine eventually cleared up to tolerable levels, though I still haven't gotten completely back to 100%. This happened back int Jan of 2009 for me. By about Aug 2009 I was on the upswing.
As for the body jerk that is waking you up, this might be related to something called "Myoclonic jerks". It's perfectly normal to experience this when falling asleep, just as you start to doze off. For instance I often stay with my kids at bedtime. The way I know they fall asleep is watching for their myoclonic jerk. I see it in both of them every night. I get it too. I had one 2 nights ago that felt like someone hit me with a taser. I hadn't had one in a long time too.
So as long as you are staying on top of the symptoms with your doc and all is cool, I would chill out.
In addition to some other issues, the same is happening to me as well.
Only response I have gotten from doctors is that it is due to the fact that I am more aware of what is happening in my chest and this is triggered by anxiety caused probably by some "real" but benign heart issues. I think the hard point is that it is most likely non-live-threatening although it is irritating.
I also tent to know as soon as I lay down if I will have a easy sleep or not. I don't know how I know it, but there's just some feeling which gives me a hint. I have been pondering if it is actually another way around. I get a feeling that it is going to happen, which causes some anxiety and that makes it to come.
I have been through heart X-ray, few EKG's, 24h EKG monitoring, physical stress test and wide variety of blood tests. All have come back normal. This Friday I am going to heart echo. After that it should be clear there's nothing serious wrong with the heart. It's just acting funny for some unidentified reason. I would recommend you to go to further tests even it is likely nothing is found, but at least it gives some peace of mind.
In my case the anxiety may be the culprit as I have been having all kinds of symptoms making my life miserable from time to time for several months now. And there's no diagnosis which starts to drive me crazy. More you follow your bodily functions, more symptoms you notice..