Beginner trying to hit the gym consistently but can't overcome gymtimidation

23M here, 5'10 and 52kg. Been crippled with social anxiety, low self confidence and self esteem for the better part of my life. Possibly adhd but not yet screened. I planned to turn it around this year starting with my physical fitness. Because I assumed mental health would follow automatically with it. But I was wrong. Turns out I can't even hit the gym consistently because my brain is hyper aware of how skinny and shitty I look especially in front of people who are way fitter and better looking than me (for some reason I have never seen any beginners at my gym?). Even though I agree that they probably don't even notice me or just don't care but I can't keep the thoughts out of my head. I've only done 4 days yet and my gym routine that the trainers gave involves first week of only warm ups for beginners like me and that just makes me feel even more stupid, seeing 19 year olds way more advanced while I'm out here stretching and doing cardio for a week like an old man. These little things are just taking way more of my mental bandwidth than it really should, sometimes stopping me from going to gym at all. Like today for example.

Has anyone here been on the same boat as me or have tips to set these aside and just focus on working out?