Yes, very definitely. Starting about 2 wks post-op, and continuing for a couple wks after that, almost every time I'd lay down, or even recline, I'd start getting palpitations. And since I can hear every heartbeat very clearly, and can also feel the palpitations very clearly, I know it wasn't just more noticeable, there was some kind of link between laying/reclining and the palpitations starting. The only thing I figured out to do that helped was to get up and walk around... Almost always seemed to help. Tried sleeping in a chair sitting up a few times, and very very slowly reclining (like a couple more inches every couple min) - had some success but not very comfortable. Not sure if the meds helped or whether I just finally healed enough that they went away, but they finally did.
The good news though (beside them most likely being temporary) is that they're not dangerous according to all the professionals I talked to. A disclaimer though, they said they're not dangerous as long as you're anti-coagulated (which I am due to my mechanical valve). So I finally was able to just relax and let the palpitations do their thing and still eventually get to sleep - but I wasn't a fan of them at all...
Oh and they gave me some anti-axiety meds which helped me go to sleep. That helped a fair amount.