Even if you don't think you look good naked---she does. If she's asking for this, it will make her happy.

In order to feel more comfortable, personally I'd suggest letting her know you feel a little uncomfortable. If you explain to her that it's stepping outside your comfort zone a little bit, but that you really want to do it to make her happy, she'll probably be very grateful at you putting out the extra effort. You could also ask her to compliment you on her favorite part of your outfit/body, so you can really feel her eyes on you.

I'm kind of similar, I don't have very much confidence in my own looks---but for me, that's only when I'm dressed. When I'm naked I feel beautiful. I think that's mostly because, whenever I'm naked with a partner, his eyes are always on me, and I can see that he thinks I'm beautiful, even if I don't. Over the years, all that conditioning has really built me up, and I feel really hot when I'm naked. Maybe your wife can help conditioning you to feel the same way. Be sure she knows how you feel, so she's sure to be caring and appreciative when you make these leaps for/with her.