I would email him, as the posters above suggest, and as kaliope says with the "hrs coincide" issue, but do go ahead with one or two sentences about the problem, and maybe asking him for suggestions? or if he has encountered this before? Just say you have a problem with responding in class due to social anxiety and would like to speak with him asap. Also you should visit college counseling to discuss this with them, and if you can make an appt with a counselor before you write to the prof, tell him about the appt, so he can make his appt for after the counseling one. That is, if other people here (or you!) think this is a good idea!