Foot tingles in hot weather and shower. brain/spine mri clear. bloodwork clear. any ideas?

Tingling: Since you don't have any other neurological symptoms I suspect that there is merely a localized area of peripheral nerve irritability that is affected by heat. It's possible that minor nerve trauma from footwear occured in the past. A neurologist is best qualified to evaluate and advise you and would be able to reassure you that this is only a nuisance rather than any serious neurological disorder