生性冷淡不热情孤僻喜静不主动
[shēng xìng lĕng dàn bù rè qíng gū pì xĭ jìng bù zhŭ dòng]
Meaning 'by nature indifferent, not warm-hearted, loner, enjoys quietness, passive,' this describes someone preferring solitude, lacking enthusiasm, and keeping a low profile without taking the initiative.