Random sharp pains in upper left arm?

Answer 1

Pins & needle sensation or tingling pain is called "paresthesias" by a doctor and means that a nerve is injured or hurt in some manner.  If you have this type of disturbance in sensation over the deltoid muscle the cause could be damage to the axillary nerve, although it could also be damage to the C5 nerve root in your neck.  If you are having these symptoms, you should go and see your physician or chiropractor for an examination and evaluation of your symptoms.  The will probably want to do some tests like an MRI or an EMG/NCS to determine exactly what is injured and how bad.  

Answer 2

Talk to a doctor this could be a sign of an underlying condition.