If class participation is part of your grade, do you need to get like a waiver for your social anxiety? Like meet with him in office hours if you can and do the exercises there. Or maybe if you super-prepare and just concentrate on learning the language, it will help you forget your anxiety. You should be answering everytime in your head anyway, when he is calling on other students (or writing the answer down). I love learning foreign languages, so maybe not the best person to answer. But don't forget to write write write - it is a necessary part of learning a language. And read out loud to yourself whenever possible, with your best Spanish accent, when doing homework. Have fun with it!