As long as I get to pick it's fine.
Without any outstanding circumstances, and assuming I can't just be a god or shapeshifter that can change race at will, I'd probably like to be a Dryad or Alruane or another type of plant monster. Being able to live without killing/eating other creatures is the important part there, so non-plants can work too.
If I need to fight; dragon, drakaina or dragonkin is a top tier pick. Nephilim(half angel/demon type) is kind of good too, but that's more likely to be the reason I need to fight in the first place, rather than the solution.
If it has to be one of the typical fantasy humanoid races, I'd rather be an Elf than pretty much any of the others.
Age depends on circumstance, again. I don't need to remember being a baby, but I'd like to experience it, I guess? It's weird to just wake up as a 16 year old and go, "Time for an adventure!" That would only be acceptable to me if I was forced into battle right away. Being a baby during a battle would be... Unpleasant.
Also, your book cover looks like Ovaries with pupils. It's kinda cool, but I doubt it's what you were aiming for.