He had romantic feelings stirring for her, but didn't dare speak.
Tips
culture
春 (spring) is the classical Chinese metaphor for romantic awakening - the season when the world bursts into bloom mirrors the heart's awakening. Common collocations: 春心萌动 (chūnxīn méngdòng, feelings beginning to stir) and 春心荡漾 (chūnxīn dàngyàng, heart fluttering). Often used in literature and song lyrics rather than everyday speech.
register
Slightly literary and old-fashioned. Modern speakers might just say 喜欢上了某人 (start to like someone) - 春心 belongs to romantic poetry, classical novels, and 言情小说 (yánqíng xiǎoshuō, romance fiction).
