I think at least some of your issue is basically the fear of stuttering. Which makes the inevitable stutter worse. Which then makes you upset, reinforcing the problem. I've had this issue almost since I could talk. I spent a lot of time with this very mindset. Eventually, I tried to stop hating myself for stuttering and getting so frustrated at it, and just accept it. This won't make everything better all at once, but giving yourself permission to be disfluent on a bad speech day, or happy about being fluent on a good speech day is incredibly freeing. Seriously, accept yourself, own it, don't beat yourself up and start out socializing with small steps (like this very post, for example!). As to whether the behavior is learned or neurological, I'd say it varies for different people. Maybe there's a neurological predisposition. In my case, if I already had that, then it was made concrete by childhood trauma and such. Like a lot of things that people debate as far as nature or nurture, we can't say for sure. But here we are. Let's enjoy life as we can. There is something to be said for speech therapy for your specific situation. It's not a question of cure, but maybe strategies and techniques to aid fluency and ease disfluency. If you can worry less about the impending stutter, let it happen, and recover, you may find it happening with less frequency.