I've had much the same problem sometimes with frequent long distance driving. Apparently there is something about the way I hold my foot/leg that causes an issue. It doesn't happen often but when it does it is a nuisance. A good massage therapist or chiropractor can help. I've tried both at various times.
You might also try adjusting the position of your chair. Are you in a cramped (or stretched) position in regards to your foot pedal?
I've decided that there may be some connection between the position of my seat and the numbness. If someone else drives my truck or I move the seat to accommodate a long legged person in the back seat and don't readjust it is worse.