My Left Arm And Hand Keep Falling Asleep For Awliile

My left arm and hand keep falling asleep for awliile and now my right arm fall asleep..while i was sleeping had to wake up shake them. I tried to sleep in a better place still doesn't work.. I workout three or four day a week for 20 or 30 mins..Still my arms fall asleep...What else can i do to make it stop?