Tā shì gè hěn shēnchén de rén, bù qīngyì biǎolù gǎnqíng.
He's a very reserved person who doesn't easily show his feelings.
Tips
usage
When describing people, 深沉 suggests quiet depth and mystery - someone who thinks deeply but says little. It can be positive (thoughtful) or slightly negative (hard to read).
