I get that too. With me it's clearly coming from my neck, compressing the C6-8 nerves. C6 is down the thumb side of your hand, C7 the middle fingers and c8 the little finger side. I mostly get the middle fingers going numb, but quite often the others, and it's not usually the side I am lying on. Solution for me is to be sure to get my pillow adjusted exactly to keep my neck in an absolutely straight position and not be kinked at an angle, which can happen if the pillow is too high.
Cauda equina type neurogenic bladder problems. Coeliac disease. Sicca syndrome. Ataxic gait and use crutches. Non-specific gut problems. Current treatment: Low dose naltrexone, low starch diet (Guts shredded by NSAIDs. Previously diclofenac worked well, not eligible for anti-tnfs, hypersensitivity to SSZ). Also short bursts of pred for bad flares