Based partially on the episode "Q2" and the obvious changes Q had undergone in it, and partially on my personal experience, the premise is that Q has spent a long time (3,000 years, but all in the Continuum timeline, so no time has actually passed in the universe's timeflow) dedicated to raising a kid and working to change the Continuum from within. And he's sick of it. And he needs a vacation. But he can't see how to step into his old life and have Picard understand where he's coming from, after he's changed so much. So he decides to create an entirely new timeline, from the ground up, parallel to the original timeline, and in this new timeline Q manifests as a woman, as well as doing some other things differently. This is intended to be a P/Q series, but since it's more or less rebuilding the TNG Picard-Q relationship first, it's going to be quite a while before any sex occurs.
Do It Again, Prologue: In which Q has a midlife crisis, dumps the kid on the mate, and takes a vacation by creating an alternate timeline.
Do It Again 2: Farpoint, Revisited: In which Q redoes the Farpoint encounter, appearing as a woman, antagonizing Worf deliberately instead of accidentally, and making other minor changes.
Do It Again 3: Quality of Growth: Post-"Lonely Among Us." Q shows up in Picard's bedroom to harangue him in lieu of giving Riker the powers later on.
Do It Again 4: That Only A Mother (Part 1): Q appears at the moment of Tasha Yar's death to offer her a deal. Not yet complete.