Tā píngshí niānhūhū de, guānjiàn shíkè què hěn yǒu zhǔjiàn.
He usually seems listless and unassertive, but he has clear opinions at critical moments.
Tips
memory
蔫 is what wilted vegetables and droopy flowers do - the 艹 grass radical on top is your hint. The reduplicated 呼呼 is a stative-adjective suffix (as in 热呼呼 'piping hot,' 软呼呼 'all soft'). Put together: 'wilted-wilted' = drooping in spirit.
register
Northern colloquial. Describes a person whose energy or initiative has gone limp, not so much physical illness.
