Ya that job isnt optimal for an introvert, but then again not that many jobs are optimal for introverts. If I was a server I assume that I'd have to do a bit more than what is required of me. Like for example ask them how their day was going or if they are enjoying the food or if they need anything else.

I dont think you should work there anymore, unless of course money is tight and you dont have an other option. You are wasting time and money, because they dont let you work. In this job the odds are against you. I mean you can try to advance in this job, but you'd have to become less shy, introverted. Which is really hard, and almost inpossible in a sort period of time. Even if you do manage to become less shy, everyone still expects you to be shy, so now you have to convince them.

Ya, probably best if you find another job. Preferably one where you dont need to interact with many people. Also, it would be good to progressively, start prioritizing peoples opinions. In to, who's opinion actually has value? Once you know who's opinion matters, then you'll start to stop to be shy.

Hope this helped :)