Be candid and share openly how energetic you are. The interviewer is simply trying to learn more about your personality and how you will fit into their existing team. The key is that you have a positive attitude whether or not you are an energetic person. You might say something like this: "I like to be a positive person and encourage my peers and work. I tend to be a go-with-the-flow person ensuring that I work hard. I typically am not a peppy personality. Instead, I like to have a smile on my face and have meaningful conversations when opportunities arise."