Yes, autoimmune disease can be exhausting and it can be confusing for other people to understand because autoimmune disease may not have obvious symptoms. A person with an autoimmune disorder may suffer from severe pain or other symptoms throughout their body but not have lab tests that show obvious problems to a physician. Autoimmune antibodies are known for a few types of disorders and those can be screened for if the lab test is ordered but not all autoimmune antigens have been identified.
Magnesium deficiency may be an underlying issue though for many/most autoimmune disorders, so taking an Epsom salt bath can provide improved magnesium absorption through the skin and allow a person to sit down to wash their hair and shave their legs (if desired). No promises though, that a nap might not still be desired after the exertion of bathing while sitting, or before the exertion of blow-drying long hair.
Fibromyalgia and chronic pain problems may have autoimmune origins  and/or may have to do with our cell’s energy workhouses, the mitochondria, running out of their preferred energy source — magnesium. They use calcium but it can overwork them to the point of cell death. In normal physiology membrane transport systems, also called ion channels, carefully control how much calcium is allowed into the interior of mitochondria. Something called ruthenium-red (RuRed)* and magnesium ions are involved in controlling the entry of calcium ions through the transport channels. [1, 2]
A deficiency of magnesium may allow excess calcium to enter the mitochondria and cause overexcitation and even lead to death of the mitochondria.
Mitochondria are actually similar to bacteria and have their own DNA that in nature always matches the mother’s mitochondria’s DNA but that is a different story.
*(RuRed) – not a nutrient I didn’t know about – it’s a dye used in labs that selectively binds with some things but not others so it is used for identification purposes with unknown samples — roughly.
Disclaimer: Opinions are my own and the information is provided for educational purposes within the guidelines of fair use. While I am a Registered Dietitian this information is not intended to provide individual health guidance. Please see a health professional for individual health care purposes.