Best way to start a conversation with him?

This sounds strange but I have a teeny tiny pet peeve with my boyfriend. We have been going out for like 4 years and I love him to death, he is perfect in every way except he is HORRIBLE with conversation. For some reason it's just me though, if he's on fb or twitter, tumblr etc and a friend posts a picture or a small comment it can turn into an hour long conversation, he'll even have long deep conversations with passing acquaintances or people he doesn't really know but I have been fighting to have a conversation with him and it's ridiculously impossible. Even if I text him, 9 times out of 10 he falls asleep and never texts back until the next day. It's just so strange...everything else in our relationship is so perfect, how the hell do I start a conversation with him? (Nothing childish or silly, we're adults lol) and does this seem like a strange problem or has this happened to anyone else?