When any extremety falls easy easily it is mostly due to nerve
compression. Excessive use of computers, too much texting, too much desk work etc, may lead to compression of a particular nerve from your neck itself. You can get some warm fomentation on ur neck, some light exercise of neck , arms and shoulders, take care not to sit for more than 20 minutes at a stretch while texting or using computers. And of course healthy diet always helps. Calcium supplements
as well as some diet rich in vit. b goes a long way in improving the condition.
hope this answer helps you.
take care. Thanks and regards.
Dr. Kartik Aswani.