Why some of us our shy and others are not

Why some of us our shy and others are not. To certain people, mingling at a party or talking to a crowded room is the stuff of nightmares. Why are some of us hardwired to be shy?
Why some of us our shy and others are not. To certain people, mingling at a party or talking to a crowded room is the stuff of nightmares. Why are some of us hardwired to be shy?