I'm 20 years old. Not the tallest or biggest best looking guy , but average built. I don't think my looks are really a problem though. The biggest problem for me is simply shyness and being uncertain about myself. I'm relatively quiet and easily don't know what to say after the "initial" opening sentences.

It seems like I miss out on the advances and don't react good enough to some girls. For example I noticed a girl staring during a college class , but I didn't find the mindset to talk to her or ask her why she's staring.

Any advice is welcome , how do I conquer my initial shyness/frightness/uncertainty ?