I get PVCs like this too. On and off. Been going on since i was in my teens. I'm 48 now and everything still works OK.
There are nerves that go from your brain stem to the heart to help control rate. There are two types. parasympathetic and sympathetic. One speeds up the rate and can also make the muscle contract harder. The other relaxes it and slows it down.
benign Ectopic beats, PACs or PVCs, are caused by cells that have something called 'enhanced automaticity' (EA). Any cell in the heart can fire on its own which would cause the others near it contract (pump) too. The SA has the fastest rate (100bpm) naturally so it usually paces the heart.
most of the other cells are around 50bpm and usually never initiate a beat, but sometimes a group of them become over twitchy. The interesting part about this aspect of the heart is that there is backup should the normal beat signal fail or fail to propagate, but I digress. But when the cells have a higher propensity to fire, this is called EA like I spoke about above.
One of the theories is that electrical signals come in from the para or sympathetic branch, that nerve signal can make a cell group with EA fire and boom, you've got a palp. This explains why people often attribute palps to a move in position, eating, exercising, sitting, standing, etc...
When the signal changes on these nerves it's called "tone". So the tone varies all the time. When you stand up, when you sit down, when you eat, when you wake up, when you sleep, time of day. you get the idea.
So the next you feel them, think to yourself that your heart nerve tone is changing, and it will eventually return to normal.
If you want, you can get more tests done. I did this. lots and lots of tests to be sure everything was OK.
My PVCs flared back in March then settled down all summer.
They flared again about 4 weeks ago. they come and go.
Thank you very much for your reply, this is very reassuring. Today I've felt a few palpitations, but already a significant improvement over yesterday.
I will likely check it out with my GP just to be sure, but you've help put my mind at ease!