Even though I'm super comfortable with nudity that doesn't mean I'm super excited to GET naked in front of people; I don't look for opportunities to show off. In these cases I was acting, in one specific case playing a really malevolent character, so my focus was already on my performance, and coming out nude adds a bit of a brain fuck. While I'm not self-conscious about my body, it's hard to separate "will my body be a distraction? will people think this is gross, or titillating, and is that actually a good thing, etc." The nudity wasn't exactly gratuitous but it was something the director wanted; it wasn't written into the role, so I was a bit in my head. Which is not an exciting feeling.
I think if I had been playing a role like Kip in Take Me Out or something similar, where the nudity and displaying of my full body like that before the audience was part of the fabric of the scene and essential to the performance to convey the essence of the character and his place in the story, then it would have been exciting. In the kind of way like "now I get to show them this power move where he combats insecurity on like 6 different levels, etc." In a scene like that I would never second guess being nude because it's literally the point of the scene.
I don't know if that makes sense.