I Have pain in my left arm it is mostly while sitting (constant when at computer workstation or when arm bent at desk) or driving is fine at night while sleeping i wake in morning get up sit a table pain starts been to hospital ER heart and BP is fine . Doing work around house pain goes away lay down 10 mnts pain goes away cant figure this out pain feels mostly muscle (sort of like muscle cramp) Is at time in shoulder or whole arm some times numb fingers most pain feels like in arm muscle