I was like that, initially. My biggest fear was that my questions or queries might be considered substandard or I might ask something that everyone already knows. I came from public schools in Nepal. I was under impression that my education was not up to par. It took me a semester to realize that my questions are just as good or even better. I used to save my questions and ask professors later after class. After constant encouragement from my professors to ask questions during class, I started it with hesitation but it is different now, I speak up when I have to. Hope this helps. -Shiv