A "trainer" can help you become less self conscious, but, the vast majority of trainers are clueless / and / or liars, and are often compensated based upon pushing garbage to their clients.
For "bodybuilding" or "physique modeling, it's all about the science and stepping into the world of chemical enhancement.
You're probably better off to study for yourself how to attain your goals.
Many trainers are ill qualified, relying on "bro science" which has no basis in science nor fact.
A really good, knowing, trainer, is going to be costly.
Different folks have different goals, and respond differently. Those are things that only your venture can walk you into, through, above, and beyond.
In my own case, I spent a year as Sagi Kaliev's training partner, working out with him several times a week when he was not training clients. Sagi has been on the cover of Muscle & Fitness more than any person alive. Sagi taught me things that would have taken me years to learn otherwise, not, so much in diet, or training, but show prep, and the chemical warfare that is national level bodybuilding. His expertise was extremely valuable, and gave me the self confidence to walk on stage knowing I was ready. For most folks, though, they don't have the discipline, money, nor the will, to take it to that level. Sagi also taught me to think for myself, when what he was telling me clearly wasn't working. It gave me the confidence to say "this is crazy to do 2 hours a day on stairs...40 minutes is enough"...things like that. Working with him was a great time, and I learned so much, but, for the lay person, I think a "trainer" is a waste of time. For competition, a mentor can make all the difference in The World.
READ. Watch videos. Watch the folks around you.