My left arm, below elbow and top side, goes numb when i am sitting. after i stand up and wait basically as long as i had been sitting, my arm feels normal again. i usually wake up with either a stiff neck or my arm is asleep but returns to normal quicker than it takes to return to normal after sitting. i try sitting all different ways, rest my arm all different ways but nothing works. i have never had any injuries, i am a 28 year old female.