What are the most common symptoms of autoimmune disease?

There may be none. There are a variety of autoimmune diseases. Some may be without symptoms - ie autoimmune thryoid disease before it becomes symptomatic. Other will have many symptoms including joint involvement, heart and lung problems in some people with in lupus and rheumatoid arthritis, rash in lupus, and dermatomyositis, muscle inflammation in polymyositis, dry eyes, mouth or other sites in sjogren's.