Happened again today. I was pain-free, inflammation-free until lunch time. Then had a big salad at a restaurant - no salad dressing, only potential offender I can imagine was the chicken which seemed somewhat processed.
Within about 15 min of consuming, I feel something's off. Not pain but a little twinge in my SIJ. Within about an hour, noticeable SIJ pain as I walk.
Just wondering if I'm thinking about this the right way - was it something in the lunch I ate, or was it something the night before, 2 nights before, etc. Is it because I'm so focused on diet, I am triggering this by sheer mental worry? But it always seems to be triggered just after eating.
@Dotyisle I suspect it's not related to my chair or sitting because this happens even when I'm eating standing up, at guest's chairs, and doesn't happen after long periods of sitting when I'm not eating
@brianzajac I am indeed in a prolonged period of stress/anxiety (going on for several years

LDN is an interesting suggestion I haven't had time to research much. Thanks for the guidance!
Thanks all for taking the time to share your experiences/responses.