What Causes Frequent Feeling Of Electric Shock Behind Left Ear And Arm?

Ive been having small electric shock feelings starting behind my left ear, down the inside of my left arm. It has happened a half dozen times in the last 6 months. The second time it happened there was two shocks within 5 minutes, I was having lunch with a friend and he noticed me twitch. It's not a dull ache it's more of an "electric shock" feeling. I've had no injuries i've got no chest pains , but it seems to be more frequent. Lately I have also been getting the feeling as if a rushing feeling to my heart..