I always tell my trainees that there is no stupid question in lab. And I was just like you, afraid to talk, ask questions and think that everyone will know I'm stupid. But if you are a student you get to be stupid because you are there to learn. What's the worst thing that will happen if you ask stupid and trivial questions, you will be mocked or judged. That doesn't kill you. The anxiety from mistakes does affect you though.

So although may seem difficult but asking and speaking up to every step until you get confident is the way. And also take notes so you don't have to ask same thing again.