I have this problem when I am trying to do "speed" training (a relative term at my age). If I stop and try to go behind a hedge, nothing comes out but as soon as I start running and up my stride length, there it goes again. As someone says, a small sanitary towel helps but I'd rather not bother.
Seems as though a lot of people suffer this! I too got a numb right foot after running about 4 miles while I was training for the London Marathon. I carried on running and it disappeared after about 15mins. I too tried lacing (New Balance 854)differently to no avail. Could it be a winter phenomenon? Because I haven't noticed it since. Funnily enough I didn't notice it during the Marathon - perhaps I had too many other things to worry about! I think it might be due to blood flow as my foot felt much warmer after the numbness went. Glad to hear it's a common problem, as I was worried that at my advanced age,it was a blood clot.