That was me too initially- the improv portion is called Table Topics and it's totally optional - it took me a long time until I felt comfortable enough to volunteer to participate. Many others choose to just focus on the prepared speeches and that's totally acceptable within TM. It's not all just prepared speeches or improv, there are many other speaking roles within TM meetings (The Chair presides over the meeting and delivers an introduction, someone else does a Thought/Toast/Joke, someone else chairs the improv portion, someone else is the Grammarian who reports on ums, ahs, etc and on the flip side, there are others who comment/feedback on the speakers but also on each other speaking role). Here's an article on Table Topics: https://www.toastmasters.org/magazine/magazine-issues/2017/oct-2017/table-topics - in the writers club, Table Topics is random, but that's not the same for all clubs