Ok, it wasn't clear to me that it was related to your positioning. So it is more like sleeping limbs? I have it all the time. I haven't found a solution for that... You're stitting down in a position that shouldn't make your legs or arms sleep, but it still does. Lately it is like I feel the blood running through a vein that is being squeezed. I have it in my big toes.
I just wanted to add something about the B12. Blood levels of B12 might be in range, but at the same time you might have a deficiency in your nervous tissue.
Many drs don't know this, and send you home with your test results that seem fine, although you might have a deficiency after all.
My B12 blood levels seem ok, but the help I get from the injections is remarkable.