"I rather thought the first move came with your proximity," Aziraphale said softly, "and...nakedness." And yes, he was still somewhat embarrassed by that, but it was hardly unexpected. He was, after all, an angel. And this was still very new to him. He was allowed to be a little awkward about it. Crowley probably had standards, and he was going to do something wrong and mess this up.
Aziraphale flushed and glanced downward. "Wanted?" he asked. "Really, my dear?" He was fascinated with the idea that Crowley really wanted him. He didn't think that there was much about him that he could see as being appealing, but he would hardly question Crowley about it, for fear that he might change his mind. He gave a startled gasp as he was pulled up against Crowley, the bite unexpected but not unwelcome. And the kiss...oh! So that's why humans enjoyed this so much. He hadn't known that something so simple was such an important aspect of human life, but now he thought he understood. And he committed himself wholeheartedly to learning more about this from Crowley.