Nope, I used to be somewhat nervous too, when someone was watching me. Not knowing where to begin, doing things slower than normal, losing my train of thought, etc... I did two things to overcome this: 1) showing people source code on my laptop while browsing, navigating and explaining it, and 2) develop new features in a coffee shop with lots of people around. I guess I found the nearby physical presence of someone distracting - but not anymore.