Assume you have all the luxuries of a modern life in your Tardis (toilet, hot showers, TV, books, game console, …) which doubles as a mini self-sufficient apartment with it’s own energy stores and generation.
Where in history would you go if comfort wasn’t an issue?
I’d go as far back as possible and see how things came to be. And to the time our sun was born and later when our moon was formed. And I’d visits the time and watch earth meeting it’s end.