I seriously doubt that it's your phone emitting any thing or a nerve problem. Sounds more like circulation. Try moving your hand, fingers and/or arm around to help get circulation back and see if that helps it go away when it happens.
hey,the problem is coming from your cervical spine and you need to do nerve stretches,look on the net,neck movements,and work on your posture(up right position)
lastly you will need to visit a physiotherapist in the near by health centre.
irene ndagire
physiotherapist