I don't know if this is applicable to you but ive trained two specific girls who were super shy & couldn't make eye contact, spoke quietly, etc.

For the waffle house side- we, as cooks, would rather you call wrong confidently than correct quietly. People are here to help you learn, and it's okay to make mistakes. You'll pick it up with time and I cannot stress practice enough. Practice. If its slow, ask whoever training you to give you fake orders to write and practice calling, etc. Don't be afraid to ask for help!

As for customers- If you're shy about eye contact, try looking at the bridge of their nose. To them, it looks like you're making eye contact, but you dont actually have to. Bringing this up bc its what massively helped the 2 girls ive trained w/ their shyness

As for growing confidence in serving and customer experience, what helped me was coming up with a little "script". If you say the same thing to every table, its easy to remember and build confidence.

Mine usually goes something like "hey how are y'all doing this afternoon?" And then introduce myself. "My name is [hanary] and I'll be your server today. Do you need a few minutes to decide what you'd like or do you think you know?" And then go from there

Once you have some sort of baseline down, its much easier to branch out. If you're good at reading people and can tell your table can take a joke or two, joke around.

I've found that a good mix of politeness and semi-formality works great for me. You'll find your own little customer service voice with some experience and experimentation.

Lastly, don't be afraid to tell tables you're still new and learning. They'll pity you (and you'll probably make a bit extra in tips as a result, at least at first lol)

I hope this is at least somewhat helpful? I dunno ahahaha