--is a very typical presentation of small-fiber neuropathy, particularly when caused by blood sugar dysregulation or other conditions that compromise circulation to some extent, as well as some autoimmune neuropathies.

Fortunately, most of those neuropathies remain predominantly sensory over time; there are very few people who experience compromised motor function.

It sounds, though, like not enough effort has been put into definitively pinning down the cause of the symptoms. It is true that investigations into neuropathy can be time consuming and expensive, as there are so may potential etiologies and even after extensive testing a good number of them remain stubbornly "idiopathic".

Still, though, take a look at these:

An Algorithm for the Evaluation of Peripheral Neuropathy - American Family Physician

Quest Diagnostics: Test Directory