But a lot of things in life make you scratch your head.
He might have scratched his head if he'd had arms to do so.
He scratched his head, trying to remember what she had told him a couple of days before.
Even so, after a while he scratched his head and put down the book.
He scratched his head and tried to remember the time.
I scratched my head and looked for a phone number on the letter.
He scratched his head, trying to make sense of it.
He stood up, scratched his head, then gave another look.
He scratched his head again and thought about it for a moment.
He scratched his head for a moment and pulled a face.
Idiome