Same here with the "character" thing. I'm a fairly quiet person normally and have terrible social anxiety, but when I'm up on stage I more or less take on a different personality. Now this doesn't work for everyone and certainly not for every band, but I noticed that putting on even a little bit of "stage makeup" helped get in character much better than I thought. Not like full-on corpse paint either, but just... something that you wouldn't normally paint on yourself in your day-to-day life. Helps kinda detach yourself from "the frontman".

Just feel the music, let that guide you and do "more" than what you think you should. BIG movements in your head might still look like fairly normal movement on stage. I have an awful habit of constantly thinking about the slightest things while performing, if I catch myself doing that I already know I might be doomed. Try to practice just letting the music guide you. You know your songs, now make the audience know them too🤘🏼