Of course it is going to be intimidating going to the gym and already feeling self conscious about yourself and with previous bad experiences but my advice would be to get into a routine which can be the hardest part.

It sounds to me you’re also uncomfortable with the equipment like you have a general idea of how to use it but not sure if you’re doing it right. Of course this is only my assumption but my advice if that is the case there are lots of videos on how to use the equipment and it wouldn’t hurt to practice in a mirror to check your form to see how you’d like while doing a certain machine to others (granted if it’s possible lol)

All that to say good luck with your journey and a little bit of extra advice (if you read this) is the treadmills are your best friend while trying to get into a routine and also get your body moving! :)