。
My hobby is collecting wristwatches.
Literal
Wristwatch [possessive-の] collection [subject-が] hobby is.
A straightforward hobby statement. 収集 (しゅうしゅう) 'collection, collecting' is the formal noun for the activity — compare with the loanword コレクション. 趣味 ('hobby, interest, tastes') is the standard word for leisure pursuits. The nominal-heavy structure (no verbs until the copula だ) is typical of defining one's interests.