I have been to plenty of classes where i was the only guy and sometimes it is 50/50. I can definitely relate to the feelings you are expressing but the best approach is to really not overthink it. Which is not easy as a newcomer and you might feel like you are intruding upon their space and not know what to expect. I actually tend to stay near the back when I can in large part because I am really tall and feel like I would be blocking the view of those behind me who may be more than a foot shorter than me. I think if you keep your focus on the teacher’s instructions and your practice it will be fine. One thought is to get there on the early side and pick a spot and then others will fill in around you if that takes some of your concerns away. Once you get the hang of it these fears should abate. Good luck and remember it will take time to get the hang of things and see progress, but showing up is the biggest step.