My husband gets up in the middle of the night and listens to music?

I've been married for 5 years now. While I would say I have a great relationship with my husband, but I can't tell if something is bothering him or not.

Over the last 7 months or so, sometimes I'll awake in the middle of night or early morning hours, and find that he's not in bed next to me.

I'll get up and go look for him and I always find him either sleeping on the living room couch or in the garage on his weightlifting bench, with headphones on his ears plugged into a CD player.

This has happened at least 12 times now.

When I wake him up, he says something that sounds plausible, but sorta like an excuse. He'll say something like "I wanted a snack, but I dozed off.", "I had gas.", "I forgot to feed the fish, and didn't want to disturb you trying to get back into bed.".

The thing is, I caught him sneaking out of bed a few times. I pretended to be asleep, waited about 5 minutes, then went to see what he was up to. In every instance, he was laying down on the couch or weight bench with his eyes closed with his headphones on.

I don't remember him owning a CD player when I met him, so I don't know where he got it from. He leaves before I do when he goes to work in the morning, and I searched all over the house for it. I found it out in the garage in shoe box by itself. The only CD in the box was Dave Navarro's Trust No One album.

As far as I can tell, that's the ONLY CD he owns. And because I recognized the disc through the transparent part of the player's lid, it's been the ONLY album he's been sneaking out of bed in the middle of the night to listen to.

I really don't know what to make of this. Should I be worried?