Hi – yes, indeed ashwagandha is best known for its anxiolytic (anti-anxiety) and stress-relieving effects thanks to its effect on the HPA axis and ability to reduce cortisol and improve sleep.
Studies on ashwagandha have used dosages of 250–600 mg/day of a root extract. The most common dosing protocol is 600 mg/day divided into two doses, with one taken in the morning with breakfast and the other in the evening.
Regarding its use with autoimmunity, ashwagandha has been found to have both immunosuppressive and immunostimulatory action, so it really depends on the individual and the state of their autoimmune dynamic. If there is concern over immunostimulatory effects, then L-Theanine, taurine, and other calming compounds and herbs like valerian, passionflower, lavender are other options to consider to help reduce anxiety.
Hope this helps.
References:
https://pubmed.ncbi.nlm.nih.gov/32021735/
https://pubmed.ncbi.nlm.nih.gov/34858513/
https://pubmed.ncbi.nlm.nih.gov/31517876/
https://pubmed.ncbi.nlm.nih.gov/27055824/
https://pubmed.ncbi.nlm.nih.gov/23439798/