My dragon Shenron does that, but it is normally when he wants out to play. However before I put up some liner (can pick it up for like .25cents a foot or cheaper from the pet stores, normally with the fish tank stuff) he would notice his reflection and go nuts, waving, bobbing, and climbing at it. After putting it up, he hardly does it anymore. So, if you have a glass viv give that a try! (I first put it on the outside of the tank, but that just intensified the reflection, so applying it to the inside of the tank only on the back and sides not the front is a better option, and beware of crickets that may try to hide behind it if everything isn't flush!)
Hope that helps!