Sporadically can’t start talking but then fine once going.

Sporadically can’t start talking but then fine once going. Hi all, New to the subreddit and wanted to ask for some advice. I am finding recently that when I need to do public speaking to an audience of people or when there’s lots of background noise eg. Wanting to get the attention of a crowded roomed, I am unable to start speaking a sentence, however once I get that first word out I am completely fine. It’s quite frustrating as I just physically can’t get that first word out of my mouth. In usual one-one conversation I’m completely fine at speaking without any stuttering at all. Thanks for any advice