I just finished my nutrition class and it wasn't too bad. I took it online and did well. I had already had A&P and Chemistry, but I don't remember those being required in any major detail in my nutrition class.
If it were me, I would take it now. Keep in mind that's somewhat biased though, because I have not yet had micro.

From everything I've heard, micro is intensive because of the amount you have to memorize. Given that, I wouldn't personally want to add another class to A&P2 and Microbiology if I could help it.
If you're really nervous about it, you can stop and ask yourself which will make you more nervous - taking it now and getting it over with despite not having chem or A&P, or waiting until next semester. Some would prefer to just knock it out and some would prefer to make sure to have those classes first. It's entirely up to you, but as long as you stay on top of things, I think you'll do fine either way.
Tiffany