I was excessively shy as a youngster and would also instantaneously blush beet red at the slightest social provocation. There were many awkward moments when I probably looked like I'd been out in the sun too long.
It took time to find the confidence to perform or speak in front of an audience. I gained some experience in my high school concert band but as the second french horn player, I sat deep in the brass section and any misfired notes were usually drowned out by the tubas.
One thing I have found helpful in gaining confidence in performing is to pause and find space within the moment. In my first experiences in a bluegrass band, our collective nerves would often translate into playing at an adrenaline fired tempo such that anyone tapping along risked dislocating their toe. Now I always start with a song I could play backwards in my sleep and really focus on projecting myself outward and ignoring the inner dialogue of fear and doubt.
On stage I try to focus externally, gathering the attention of the audience and working on building a relationship with them. The intensity and intimacy of that relationship varies depending whether it's a small group around a lakeside campfire or a raucous bar crowd but you can almost always make a connection with at least one person and build from there.
Building confidence and stage presence is still a work in progress and I need to find more opportunities. The biggest step is letting go of the inner fear and focusing outward to make a human connection. The same process would work whether it is overcoming a fear of one on one social interaction or getting up on stage in front of thousands.
Like most worthy adventures, it just takes intent and practice..... I think.