What you may not realize, and what I would tell anyone going for an interview, is that it’s important not to bore your interviewer with overly long answers that are not relevant. That is a major no-no, for me anyway. Please do not worry about being shy, though. It’s a common trait and simply part of who you are. But if you want to learn how to compose yourself when feeling nervous, a useful tactic is to simply pause for a moment before answering a question. Seriously, it works. This will show you’ve really listened to the question and are being thoughtful in your response. Then, try to answer as succinctly as possible – perhaps giving one or two examples of something relevant to illustrate.
It’s also fine to admit if you do not know something or can not think of an example on the spot; it shows you’re neither a robot nor a show-off. You might be able to think of an appropriate answer at the end of the interview or even follow up with the answer afterwards. Believe it or not, this could make you memorable. Another tip, which so many people do not do, is to maintain eye contact and speak slowly and clearly. A chatty person may be enthusiastic, confident and extroverted but can also run the risk of losing the patience of the interviewer with their babble. Trust me, your shyness will not be held against you if you speak with substance and honesty.
Remember, your CV has put you in front of them so try not to repeat too much of what you’ve already supplied in writing. They’re looking for what you are offering that makes you unique. And, lastly, if you do not succeed this time, I know it’s disappointing but try to spin it as a helpful experience in helping to get the interview ball rolling for you again. You can ask for feedback from your interviewers and (ideally) throw yourself more enthusiastically into applying for other opportunities in the future. Good luck!