The “pins and needles,” numb feeling in your arm is known as capillary crush and occurs when there’s too much pressure on your blood vessels, worsening your blood circulation. Some potential causes of capillary crush include carpal tunnel, thoracic outlet syndrome (TOS), nerve damage, vitamin B12 deficiency, certain medications, and an awkward sleeping position. If you believe a health condition is causing your dead arm, speak to your doctor for assistance. Otherwise, switching to a sleeping position where your arms aren’t compressed can eliminate the numbness.