Walking sounds mechanical to me...as opposed to standing which could be pressure from blood pooling in the foot or from swelling.

I would pay attention to what part of your stride is setting it off and that could give a clue. For example, I have surgical scar over my calcaneal and pretty much no fat there from trauma. When I heel strike and my foot is dorsiflexed I sometimes get a zinger where the nerve is pulled across a bony prominence.

Pinpointing the part of the walking motion might tell you if it is a stretch issue or a pressure issue.

As for the spine, I of course can't say, but it does seem intuitively that you might have additional symptoms if that were the case.