I would very much like to find out what condition this is. I think I have the same thing. Mine started probably around 11 or 12. All of sudden I just couldn’t make sounds when I was nervous. It’s like a paralysis. I just lost control of my mouth. The words were just behind my throat, but they wouldn’t come out. Later, I found out I struggled especially with words that began with “ex”. To this day, I say “escuse me” instead of “excuse me”. If I try to pronounce the “ex” sound, I just lose control of my jaw. I would open my jaw for the “eh” sound but couldn’t close it for the “x”. So frustrating! It happened most frequently when I was nervous, which was why I associated it with stutter. I was weird. I could speak perfectly in public. I did speeches and debates in school. For some reason, this condition really affected me when I talk one on one, especially on the phone when I couldn’t see whom I was talking to. So I have learned some coping mechanisms, such as leaning back in the chair to force my body to relax, or talking like I am giving a speech instead of one on one. Most people don’t notice this anymore because I got so good at hiding it. Every now and then I catch myself saying “for instance”, instead of “for example”, when I feel that paralyzing feeling creeping up. It is not typical stutter, where you repeat or make sounds. This is just no sound at all. I never sought professional help for it. I hope you would. Let me know if you found out what it is.