scratch one's head

Much of the rest of the list leaves one scratching one's head.

One can only scratch one's head in bafflement.

A strict constitutionalist might indeed say that the constitution died in 1861, and one would have to scratch one's head pretty diligently to refute him.

"Contains the famous accusation that forcing bids are equivalent to scratching one's head or blowing one's nose to convey information."

"If you look in broad daylight you can't see to the end of the street, and there are side-streets, too, and one can do nothing but scratch one's head.

It might be socially unacceptable scratch one's head in public, and the fear of unattractive flakes in the hair or on the shoulders can make some uncomfortable and self-conscious.