I've experienced the same problem.
I remember a long time ago asking my sponsor for help. Like "What should I say?"
He told me:
#1. Always be sure to remember to welcome the newcomer, to help them feel comfortable to be there and to let them know that I care about them -- and let them know the how and why that AA has been good for me. And, what AA sobriety has done to improve my life.
Then, if I have more time to share: Just tell them what I was like, what happened, and what I am like now. Also, be sure to let them know why I keep coming back.
People do things for their reasons and not mine. If I knew what their reasons were -- it would be easier to talk. I've discovered about myself, that often -- I don't even know the real reason that I'm doing something, let alone their reasons. I'll think I know my reason -- but, then discover later on, that my real reason -- was not the same as the reason that I thought it was.
Thanks for sharing! I like your topic, because it's something that always interests me. I've nearly always had difficulty in speaking.