That’s interesting as I had the exact same symptoms off and on for years. I would have numbness in my left thumb, index and middle fingers when sleeping on my right side and vice versa. Roll over on my back or the other side and it would clear almost immediately.
I tested borderline anemia which was probably false, sports anemia. But my doctor told me, a late 60s man, to take an over the counter pre-natal multivitamin which has more iron and a couple of other things.
I have been taking it for several years now and just now realized I don’t have the numbness.
My bicycle has the correct width handlebars that keep the wrists in line to the arms, this plus resting on the edge of the palm heel prevents median nerve compression. Yeah, this is off topic, but thanks for your post. Maybe it’s vitamin D3 or some other vitamin/mineral deficiency that the prenatal vitamins took care off.
The last year my labs have included quite a few vitamin level tests and they are all within range now, as are hemocrit and hemoglobin.