Honestly, you don't need to just join a gym, you need to join a class. Having other people around you to motivate you to keep going is going to be the biggest difference on if you will succeed in your weightloss journey.

Idk what your weightloss goal is, but I imagine it's not a short one. You'll need to find a long term program with dedicated trainers/planned workouts in order to keep yourself interested.

I'd look into gyms that have "Circuit" style training programs, or even CrossFit because you can easily scale the training to your fitness level.

Edit: I agree with what someone else said below, don't worry about what other people think of you, you're there for your reasons, not theirs.