When I took up running again a couple of years ago I regularly experienced numbness in my right foot. Like Sheila, I would get pins and needles after running about 4 miles. The pins and needles would then usually climb up my leg, sometimes reaching my thigh, but by about 8 or 9 miles it would clear up. I did also get numbness in my left foot but not as frequently or to the extent as that in my right foot.
I tried several pairs of running shoes and varied the way I tied my laces but it didn't seem to make a difference. However, I did feel that it was related to factors such as the speed at which I ran, incline/decline and camber - I tended not to get it if I ran slowly on flat surfaces. Incidentally, my foot would only ever go numb when I ran. It didn't seem to be affected by other sports, like 5 a-side football.
In the end I went to see a physio and after him ruling out my footwear and running style concluded that I was "stiff as a brick" - his words not mine! He thought that my calf muscles were particularly tight, which meant that I wasn't absorbing the shock effectively when my heel struck the ground. (Don't ask me why this should give my pins and needles). Anyway, he gave me a number of exercises to do which concentrated on stretching my calf muscles, quads and hamstrings which seems to have done the trick.
Hope this helps.
S.B.D.