picard120,
Unless you have a specific speech impediment, I would probably pass on speech therapy. A better (and more fun) option might be vocal (singing) lessons. With a quality instructor you will learn how to improve both your singing and talking voice.
Also, pass on the JFK sound-alike stuff. You don’t want to sound like someone else, you want to sound like a “new and improved” you. This is a critical priority with a good instructor. You do not want to change your voice to sound like someone else, but cultivate and optimize your own voice. You want the politicians and other pulpit pimps to say, “Man, I wish I sounded like picard120”.
Focus on proper breathing and voice projection can also increase your energy and while calming your nerves. It really is an interesting art/science.
I was fortunate to find an instructor that had a Yoda-like teaching style. Some of the practice was comparable to forms of meditation. You don’t have to perform or ever sing a song to benefit from vocal lessons.
Cheers, TR