Sorry it took forever to get a reply, but I just read your post, and am here to say I too have a late onset stutter. I developed mine when I was 28 (am 34 now) and I also suspect it correlates with a burnout I was going through. I was later diagnosed with ASD at 32. I haven’t found conclusive evidence of this, but suspect there is a connection between autistic burnout, and stuttering. I work a very stressful job that basically leaves me in a constant state of burnout. As a result my fluency really fluctuates. Some days I can speak at 100%. Other days I block on almost every other word. It’s difficult but I’ve learned to live with it. Speech therapy does help fortunately. Hope you see this, and it gives you some comfort. You’re not alone in this for whatever it’s worth!