I think social confidence often get confused with introversion/extroversion. Introversion isn't about whether or not you are a shy person, though shyness is often a function of introversion. Introversion or extroversion are based on levels of cortical arousal in the brain. Introverts tend to have a high level of resting arousal so are easily overwhelmed by loud noises, new situations and sudden movements, which tends to make them a bit more retiring but not necessarily inherently "shy". However extroverts don't have a lot of resting arousal so usually seek stimulation from their environment, often through outgoing behaviour.