I think it's normal, especially given your age and lack of relationship experience. However, it sounds more like you are afraid to be vulnerable, rather than nervous to be intimate with this person. You said so yourself that you are confident and outgoing, so you are probably holding onto your pride too tightly. What kind of conversations have you had with this person? It's possible that you two are very different people, with not a lot of common ground to talk about. That can happen, and it doesn't necessarily mean it's a bad thing. It could mean that you need to be more open to other ideas and topics to keep the conversation flowing. Are you more inclined to ask questions, or answer questions? Maybe next time you know you will be hanging out with her, prepare some questions, or topics, that you can bring up in conversation with her. That way you won't trip over your thoughts when you try to talk to her.
"Caring is not an advantage."