Totally normal, so no reason to fret. But there are things to do about it that are reasonable, too.
Men who are physically active like playing football or basketball on a Saturday morning will find their sex drive revved up that evening. It's a natural by-product of testosterone. So his guy friends can help your sex life, how funny is that?
This is different kind of day, duing the week you're drained from all the day's exertions and sex may not be the relaxing thing it might've been 10 years earlier, it can feel like more work.
Also, naked is over-rated. Even if you're gorgeous naked, guys visual nature means you spice it up by hiding it and revealing in freaky ways. During intercourse, your nudity will greatly enhance his pleasure, but nudity as foreplay is misplaced.
Get his engine running by doing things to poke him sexually in situations where you would never normally do so...
- rub the inside of his leg at the table in a restaurant but above the table act like it's not happening (especially great if there is someone at the table with you)
- stand close in front of him and rub him with your hand behind you while riding in an elevator or escalator... on an escalator, make him follow you up and down the escalator a couple of times while you do this...all the while talking about something else. Funny!
- take him to his favorite sporting event with a blankie and massage his privates under a blankie during the game.
- wear a totally loose fitting blouse and visit him at work, be sure to bend over SEVERAL time to accidentally flash the goodies.
- riding in the car, absentmindedly stroke his hair, head, lobes...not sexually, just touch him (lots variations on this...touching him lovingly in public a lot can pay off later that day)
- we're Christians, and my wife once jumped me AT the church (no service was going on), dragged me into a closet and we got it on. Oh my!
Sex can be fun, and same time every week in the same room in the same routine is, well, routine. That's fine if that's fine, but if it's not, you can fix it, have some fun. He'll pick up the game and start some tricks of his own. If he doesn't, that's ok, you keep doing it. Still fun.
Oh, in addition to the litany of ideas above, just a note - you might consider some "start of day" initiations, too. Men frequently wake up in a heightened state of sexual stimulation (still sleepy, though) and morning quickies make a great way to start the day.