RidingRollerCoaster, I think I have had the same thing. Lying down to go to bed, I feel these strong jolts of pulse all over my body, sometimes in my head but often in my chests and even the peripherals. I noticed that when I woke up it wasn't there but when I would go to the bathroom, come back and lie die it was back, my heart was thumping hard, not a nice feeling.

I think in my case it was partially to do with loss of physical condition, like just the act of getting out of bed was enough to cause my heart to race. Otherwise I have zero idea what caused it for me. It has improved recently, which also corresponds with improvement in my anxiety, perhaps these were linked.

This has also gone now too of course, but when I would wear ear plugs, I would feel my heart pulsing in my ears. Made it rather hard to get to sleep