I'm the same way. Quiet, sort of shy. But I have always been like that. Frankly, I am upfront about it and say early on , " Look, I'm a bit shy and uncomfortable with people I've just met. I might be quiet or seem aloof. But, it's me, not you, Once I get to know you I'll talk my face off, and once you get to know me, I guarantee you'll love me."
Its really always worked. People get it. Spells it out for them. Oh and of course, being high always helps. Even if its to your head.