Have always been told that numbness is a certain sign of a nerve being in a bind somewhere. If it's recurring to the point you know when it's coming, then that nerve is repeatedly getting pinched. This is not to be fooled around with if one wants to continue doing what you're doing. Could be in a minor joint, could be in a spinal situation. You need someone trained and knowledgeable to diagnose and treat the situation appropriately, or you'll be dealing with that numbness on a permanent, daily basis. How will you do your work then? Good luck, I hope it's a minor issue, an easy fix.