Carolinemc and Eva - thanks for your input.
I use an Apple Watch 7 to track my sleep, breaths, and blood oxygen levels. I'm not sure that I have a lot of confidence in its determination of this factor during my sleep - last night, it showed 98% oxygen levels, during the last month, it varied from low-to mid 90s, to higher values. I get the feeling that it may be underestimating, depending on how I'm wearing my watch when it tests my blood oxygen.
I've been drinking Ovaltine for years - it doesn't seem to effect my heart rhythm. For a few months, my PVCs were gone - now, they're back. I'm not sure why. I don't think caffeine has anything to do with it.
I used 1/4 - 1/2 tsp of instant cold brew coffee in my Ovaltine, but stopped. I doubt there was much caffeine in the coffee. After dinner, I have a few belgian cookies - these have some chocolate in them - with my wife. These may have some impact - I didn't have this problem until I started eating them - Maybe I'll convince my wife that I don't like them (probably NOT implicating an effect on my heart rhythm) and stop eating them. Maybe staying away is all I need to get my rhythm back.
FWIW: did you know that 'decaf' still contains caffeine? It just contains LESS than full caffeine coffee.