How does a more introverted guy express interest in a girl?

I'm in a situation where I feel like he may return feelings for me, but he's not showing it or going out of his way to talk to me or spend time with me. we're friends so we do hang out pretty regularly with a mutual friend of ours...the last time I saw him was Sunday though. I don't want to give up on him because he doesn't know how to show someone he likes them. he was a hermit before he knew I liked him so it doesn't surprise me that he's still a hermit after we've hooked up. it's just making me think too much. so how do introverted guys show that they like someone if they're almost completely reclusive?