Totally normal.
I've been in sales and marketing for most of my life, lot of talking and expressing ideas for a long time, but as soon as I got sober and into AA, I "clammed" up BIG time.
It's crazy, BUT...I treat the rooms of AA like practice. I want my confidence and public speaking back and I think practicing, by speaking and expressing myself, at AA meetings is perfect. It helps keep me sober, maybe it'll help someone else, and I'm getting better at speaking in groups (I think...).
In saying all of that, I also don't force the issue. I don't talk at every meeting and that's ok too.
Do you ever chair any meetings? That's a great way to get involved and all you have to do is read a script. It'll help with your sobriety too.
Kjell