One of the hallmarks of a great speaker is the ability to remain poised and unshaken in the face of unexpected distractions that often occur when addressing a live audience.
The reality is that whenever you speak, inevitably someone's phone will go off, people may interrupt you to voice their opinion, and often people will walk in and out of the room. All of which can easily throw your focus off and cause some anxiety.
In order to condition yourself against these distractions, an effective strategy is to intentionally prepare by placing yourself in environments and situations where you can train yourself to handle these scenarios simply by practicing being exposed to them in low-stakes stakes situations.
I suggest that you put together a short 20-minute presentation on your topic and approach organizations like the Rotary, Kiwanis, and local Meetup groups and offer to share your knowledge with them during one of their weekly meetings. (they are always looking)
One particularly memorable occasion for me was when I did a talk in a restaurant for a rotary group. The position where I was set to speak from was right in front of the two-way swinging doors to the kitchen. Throughout my whole presentation, waiters were constantly crisscrossing in front of me in order to deliver food and take orders from the audience that was sitting in front of me. Although challenging at the time, that event, and others like it enhanced my ability to successfully keep focus and work through distractions that have come up during high-stakes presentations.
So, in short, seek out opportunities to practice in front of low-stakes live audiences where the environment is not controlled so you condition yourself to be able to work through distractions so you can remain poised and focused during high-stakes presentations.