He enthusiastically started telling stories from his childhood.
Tips
memory
勃勃 is a reduplicated form meaning 'vigorous/flourishing' — think of 生机勃勃 (bursting with life). 兴致 = 'mood/interest', so 兴致勃勃 = 'bursting with eagerness'.
grammar
Typically adverbial: 兴致勃勃地 + verb. Describes how someone does something, not a quality of the thing itself.
