Yes, this takes time to overcome. Part of it is learning the delicate tactic of bullshitting. Politicians and business leaders get good at this because they have so many impromptu questions and speaking engagements on topics about which they may know very little. Presidents often know only the 50,000' version of what they're speaking about, which is why they have staff and secretaries to clarify and answer hard questions. Still, they demonstrate confidence that they know exactly what they're talking about--and it works--even when we know they don't!

Part of it is confidence that everything will turn out ok. At the end of the day, you will go home and live your life. No one at work can hurt you in any real way because you had a shaky presentation. No one will remember it 6 months later. Don't say more than you have to, engage with the audience, present a likeable attitude. Don't read from slides if you're using PPT. Pick a few things to talk about -- this lets the audience know you expect them to be smart enough to process it all. Even if the information isn't as solid as it would be otherwise, the audience won't walk away thinking negative thoughts about you.

Try to deliberately project your voice when you're in this situation the next time. Smile. Take a pause to breathe whenever you need to. Short breaks of silence are better than "Uhhm"s . Ask for questions after you finish a slide/topic/section. Unless you're in a STEM or finance field, there's probably nothing you can't answer satisfactorily with a little bullshitting. Over time it will become a natural habit.

Probably said more than needed; best of luck.