Depends how long the time loop is. Hopefully not like 6 seconds, but a day.

If it was a reasonable amount of time in the loop, I would start learning everything I could, like languages, stem topics, etc.

But I would also try to experience as much as possible. Learn how to speak in front of crowds, how much of a pain tolerance can I have, fear of heights, that sort of things.

Basically imagination is the only limiting factor.