I can definitely relate. A couple beers or cocktails and I can be the life of the party. Hell my Spanish speaking skills even goes from basic (maybe 1st grade) to something more reflective of someone that took 6 years. One thing that has helped is I created an alter ego that has the same confidence as my drunken self. Before situations where I have to be social I “transform” into him by asking myself how or what alter ego would do and play it out in my head a bit. Later I found out that during a business class at UChicago that this similar to Harry Davis’s Learning from Experience where you experiment with different characters of yourself. Some people call this faking it till you make it but I think it is deeper than that. It is pulling out different aspects of your personality (some you didn’t even know were in there) and developing it through experimentation and reflection. Good luck OP!