To the best of my memory the very first time I was ever asked to speak without notes on a subject was in high school during the inter-house music and drama festival. The scheduled speaker grew cold feet and I was asked to speak, I forget the subject but am pretty sure I still have the certificate because guess what, I won in that category.
As life has progressed I have had numerous opportunities to speak in public. And sadly along the way I lost the art of speaking impromptu on any subject. I now prefer to research, to study, to write down my speaking notes and follow them through on d-day. That has become my comfort zone, the place I have been flourishing in for most of my adult life.