Any autoimmune disease that affects autonomic function or PN can present with your symptoms. But there are also other causes of autonomic dysfunction & PN, like diabetes. Actually, diabetes is more common to cause PN and dysautonomia then autoimmune disease.

Have you had your blood glucose checked? What about a glucose tolerance test (the long one)?

Do you have any other odd symptoms that might point in a direction of a particular autoimmune disease...like malar rash, joint pain, profound fatigue, dry mouth or eyes, joint redness or swelling, etc?