Let me preface this with acknowledging that I am someone who many of you being shy would probably view as outgoing, aggressive/assertive, thinking out loud type (although when people learn that I am really an introvert, they are surprised). I think all of medicine requires that we learn to read people- our patients, our colleagues-- and adapt accordingly. Talking too much or too little are both problems.
No matter what your personality type some attendings/residents will like you or find fault. It depends on the team dynamic. It can be very hard to adjust- I speak from experience on this one in needing to tone down my enthusiasm and energy at times so as to not overwhelm a shy or just busy attending. If I feel like I am asking too many questions (usually a feeling from observing non-verbal communication), I go read about it instead. I might even make myself scarce for 20 minutes if there is too much face time.
As far as looking interested in learning, it is true that an outgoing student will often appear more enthusiastic and knowledgeable. I am willing to go out there on that limb and offer an A&P without being asked, I will ask questions about why one thing was chosen over another on rounds. However, I do not think it is a lost cause to get fantastic evals in clinical rotations for those students who are not as comfortable being outspoken. I would seek feedback weekly from your teams.
I think there are also other ways of participating that would be in your comfort zone, i.e., bringing in articles for the team on your patient that outline the latest guidelines, offering to teach the team on a particular topic (allowing you time to prepare and not go off the cuff).
Also, be upfront with your team. Explain that you are a little on the shy side but very interested in what they have to say and if they have any suggestions for you to improve you would greatly appreciate it. Sometimes practicing your presentations can help with the appearance. Maybe have a goal that you share with the residents- I would like to ask 1 question per day on rounds to the attending- have them assist you with getting out of that comfort zone. They might even suggest a particular insightful question.
Good luck.