I've done a lot of pair programming but I'm probably not much use as I never really had an option not to like you did. In my first job we had to pair program, everyone in our team did. I was a recent graduate and quite quick to learn but I still had trouble sometimes at first. But it was the pair programming that helped me along and made me feel more comfortable that what I was doing was correct. And after a while I realized that the more experienced guys were the ones I wanted to pair with most, not avoid, as I could learn the most from them.
You have to realize your own limitations, those experienced guys will know you are less experienced, they're not going to punish you for it. I would say forget your worries and dive straight in. But don't behave as if you're under test, you're not. Be easygoing, ask about things you don't understand, and be prepared to accept you are wrong sometimes. Now as a more senior developer, there is nothing more annoying than pairing with someone who is afraid of being wrong - it just becomes really awkward. I did some pair programming interviews (which were actually tests!) but the worst guys weren't the ones who used Google for everything, asked me loads of questions, or said 'I need to think this through a bit'. Those guys got on quite well. The worst guys were the ones who sat there and suffered. The ones who thought they should know stuff so shouldn't Google it or the ones who panicked when they couldn't understand stuff at first shot and just went really nervous and kept saying 'Um' and 'er'.
Your ability to think deeply about things will probably be an asset in pair programming - thinking about upcoming problems as your pair solves the immediate one, or coming up with a better thought-through solutions, seeing extra edge-cases your pair didn't etc..