The fact that socializing comes easier to you when you've had a few drinks tells me you're better at socializing than you realize but something is impeding you from being your true self in certain social situations. Sometimes certain scenarios can trigger fear/anxiety/self-consciousness. It's like the trigger sparks memories of past trauma that we have to play out again and again. I had a bad experience in grade school when I had to recite a book report in front of the class. I froze up there and that stayed with me for a long, long time. Practice is the only thing that helped me overcome it. I'm think I'm good at socializing now and making small talk and can speak in public but it's not my favorite thing to do.