I think it's a personality trait, not easy or even possible to overcome. But it gets better with time as you gain experience. For instance, talking with your su

I think it's a personality trait, not easy or even possible to overcome. But it gets better with time as you gain experience. For instance, talking with your supervisor may be hard now, but will certainly be easier in six months. And in two years, your supervisor may be the one asking you questions and seeking your expertise. And you're not alone in this. Some people may appear very confident, and as you get to know them better you realise they are struggling too.