Social anxiety disorder, also known as social phobia, usually starts in the teenage years, and can last for several years, and in some can last for decades. Social anxiety can get worse with age if you choose not to deal with it. This is because if you choose not to deal with it, then you do what comes naturally with social anxiety, which is to avoid social situations so that you don't become so anxious. However, when you keep avoiding social situations, then this just maintains your belief that you may embarrass yourself or that people may make fun of you. If you keep avoiding social situations, then you never get to find out that just exposing yourself to social situations is not that bad afterall, and with time, the anxiety goes away with repeated exposures.
So in summary, social anxiety gets worse with age if you don't deal with it. To learn more about social anxiety and how to deal with it, please watch the following video: