Probably mine is not really a "shutdown", but I can very easily get nervous around people and I start shaking. If I try to speak in that state, my voice will be very shaky as if I were being emotional and about to cry or something. I surely can't say what I want to say in that state. It's rather embarrassing to let others see me like that. So in whatever situation, if I have to discuss something with others, such as in a meeting, I always end up not being able to argue my points. So, I always lose. I can never get my message across because of that. People don't take me seriously. It's very frustrating. I've been like this all my life.