I also suffer from an onset stutter. Mine started at the end of a very traumatic battle with alcoholism. I have no specific event I can connect it to when it started, and think the overwhelming amount of stress I was under caused me to start stuttering. I’m still dealing with it 3+ years later. Sometimes it clears up completely, or near completely. Other times I have a really hard time with it. I’ve def seen a connection with stress/anxiety, and how bad it is. I also suspect I suffer from undiagnosed mental health issues such as depression, and ASD that might be linked to how it started at such a later age. Unfortunately there’s not a lot of info out there on acquired stuttering, and much less the psychogenic form of onset stuttering. Most cases I’ve learned about are connected to head trauma, and a TBI that cause the stutter. Other than people posting on here I hardly ever see anything about a stutter starting “out of the blue”. I hope you find answers, and learn to live with, or manage your case. Hope this helps in some way