Hello cause can be Vascular - There could be some reason for poor circulation to the arm/hand. This is very commonly caused by too much muscle tension in the scalene muscles or the the pec minor muscles. The blood vessels that supply the arm/hand have to pass through these areas, via the subclavian artery, to branch off into the arm. It could also be due to a misalignment of the shoulder. If a shoulder is misaligned in external rotation, it can put a stretch on the blood vessels that pass through that area to supply the arm/hand. Pinched nerve either in your neck, shoulder, or arm. Warning signs when you need immediate consultation with another specialist neurologist Tendonitis Migraine (hemiplagic migraine) Stroke, Transient Ischemic Attack (mini-stroke) Chronic Fatigue Syndrome/Fibromyalgia Reynauds disease causes constriction of the blood vessels and usually your fingers get numb, turn whitish in color. Angina