Hello @dansweeney, Welcome to Connect. You mention that your leg muscles burn even after a short walk which I think can be a symptom of nerve damage from Vitamin B12 deficiency. Here's some information on the topic:

" Trouble walking. Over time, peripheral nerve damage resulting from vitamin B-12 deficiency can lead to movement problems. Numbness in the feet and limbs may make it hard for a person to walk without support. They may also experience muscle weakness and diminished reflexes."
-- 11 symptoms of vitamin B-12 deficiency:
https://www.medicalnewstoday.com/articles/324265
A neurologist normally diagnoses nerve damage. Do any of these symptoms similar to the ones you are having?