I remember when I first started exercising, I was a fat alcoholic that was usually the youngest person there and had no idea what he was doing. I was very anxious about potentially doing something wrong, or being taunted or judged. I didn’t know how to use a lot of equipment and it took a long time before I even realized kind of “obvious” stuff like you being able to swap out attachments on cable systems. I knew my body language was glaringly displaying low self confidence and anxiety, and was further psyched out by knowing that it was obvious and I couldn’t do anything about it.
As I went to the gym more I became more self confident and also assured through experience that I wasn’t doing anything wrong and nobody would be a dick to me. I mean, people are dicks sometimes, but usually only out of their own selfishness (like wanting to use something you are, or hogging something they’re not use because of fucking supersets), not malice. There’s always a small chance of a bad interaction along those lines every time you go but the anxiety definitely greatly subsides over time.