My boyfriend is always so animated and talkative; why does he get so shy and awkward about intimacy?

Alright, I have a question about my boyfriend, Joey. He’s 25 (I’m 23) and he’s a very… Interesting person. Now don’t get me wrong with anything I’m about to say; he’s an amazing boyfriend. We’ve been together for almost 3 years now (We live together as well) and I love him more than anything. He’s such a kind, caring person, and he actually understands my emotions and listens so well and can always make me laugh, even when he’s not trying to. I just couldn’t ask for anyone more amazing. :) Anyways, he’s a very interesting person. I find that after almost three years of us being together, he’s still sort of weird about certain things. Sometimes, he acts sort of shy and awkward about intimacy. Sometimes he even acts like this when we’re cuddling and he’ll move his arm around me or something and he’s just so reserved about it. Also, sometimes when either of us initiate sex, the foreplay is a lot of him being sort of awkward and shy and making jokes to try and cover that up.

He’s not an awkward person any other time; he even acts and sings so he’s not really awkward at all. He’s very charismatic, so to speak, and he’s very animated the rest of the time, which I love about him. He also had two serious girlfriends before me, so it’s not like any of this is new for him. I just don’t get how he’s so talkative and lively every other time, but once we get intimate in any way, he gets shy and awkward. I mean, don’t get me wrong, there’s nothing wrong with what he’s doing. We have a great sex life and as I said, I love him more than anything. I’m curious why this happens. Why would he act like this?