* It could be a shortened form of a phrase: For example, "Sometimes yes" or "Sometimes you".
* It could be a placeholder in a sentence: Perhaps you're trying to recall a specific word or phrase and are using "Y" as a temporary placeholder.
* It could be a typo: Perhaps you meant to type something else entirely.
To understand the meaning of "sometimes Y", please provide more context.
For example:
* Where did you see it? (e.g., a conversation, a book, a website)
* What was the surrounding text?
With more information, I can help you figure out what "sometimes Y" means.