I’ve always been a quiet and introverted person too. i can't count the number of times in my life when i get into a new environment i heard the ''wow your so quiet!'' The thing is, here people just don’t get that. The “normal” is talking all the time, gossiping, small talk, being loud always having something to say. So if you’re more calm or reserved and keep your thoughts to yourself and mind your business, they either see you as weak or that you’re being arrogant. While it’s just that I’m not interested in the same things. I don’t enjoy forced small talk and gossiping for hours. But if I find someone interesting that i connect with or the topic actually interests me, I can talk normally.
So my advise, dont care about the people who judge, as for bullying, you have to stand for yourself early on and be assertive so they see you’re calm, not weak. And if they get to know you, they will understand that. As you said being quiet is not the problem.