Hard pass. 
The author has the intricate, monumental job of thinking about plot details, character arcs, who knows what when, etc. Until the story is down and relatively solid, try not to let your brain get distracted by “what’s a better way to say this?” or “does a comma belong here?” Resist the urge to look up the correct spelling and you’ll be rewarded with a brain that focuses on how to reveal the secret that changes everything.
There are multiple layers of developmental editing revisions where we work on bringing out a cohesive story. Then, and only then, do we tackle sentence structure, punctuation consistency, and such.
Enjoy the writing process, and don’t worry—I’ll help you through the details later.