Low iron can commonly cause numbness/tingling in the arms and legs, and the arm go numb while sleeping.
I had the same symptoms as you and started taking Blackstrap Molasses - 1Tb morning and night, as will as a plant based iron supplement(garden of life).
Plus plant-based vitamin C to boost absorption of the iron.
Soon after taking the plant-sourced iron all my symptoms of numb arms after sleeping and gas and bloating all went.
I would also sometimes get a little but dizzy or foggy and that went too.