Per its title, Psalm 34 was written when David pretended to be insane before whom?

Answer: Abimelech

The title says David wrote it "when he pretended to be insane before Abimelech, so that the king drove him away."

“Of David, when he pretended to be insane before Abimelech, so that the king drove him away. I will bless the LORD at all times; His praise will always be on my lips.”— Psalm 34:1 (BSB)