I bought new footwear a couple of months ago and started to have slightly numb areas under my foot - was a bit concerned, but it turns out it is the foam or whatever under the covering which has collapsed so there are ridges across the sole, under my foot and pressing on soft places. I wore some jell innersoles yesterday and today the feeling is much more normal - so do check for that sort of problem first.
If you do not have such things already and you are walking on hard surfaces, the innersoles do make a big difference to foot comfort anyway.