How do you describe this body position?
My best guess is "man putting his hand on his head" but I know there's something less gothic than that.
He is resting his head in his hand.
From The J. Paul Getty Museum
Woman resting her head in her hand
That's called propping.
Prop (verb): [with object and adverbial of place] Support or keep in position.
Example: She propped her chin in the palm of her right hand.
— Lexico
In your picture, he has propped up his head on his hand.
