Why does my dog whine at my closet?

I have a 2 year old Sheltie that suddenly developed a habit of whining at my closet. He really goes at it too, he whines really loudly and sometimes wakes up the family at night. I’ve tried to look through my closet to see what he wants but whatever I take out, he’s just as equally interested. He sniffs my clothing and tumbles around in them and when he finishes, he whines at my closet again. I’ve also tried shutting the doors of my closet and closing him out of my room, neither ones deters the whining. Please, if anyone’s got any clue of what the cause is or any advice, I’m all ears.