Tā wúyìshí de yǎo qǐ le zhǐjia, zhè shì tā jǐnzhāng shí de xíguàn.
He unconsciously started biting his nails - a habit when he is nervous.
Tips
usage
无意识 can describe an involuntary action (comparable to 不自觉地) or the psychological 'unconscious' mind (as in Freudian 无意识/潜意识). In everyday speech, 不自觉地 (bù zìjué de) is a common colloquial equivalent for unconscious/involuntary actions.
