At the beginning of Act V, Scene 2 of Much Ado About Nothing, does Shakespeare insinuate that anything is going on between Margaret and Benedick?
The beginning of Act V, Scene 2 of Shakespeare's Much Ado About Nothing starts off with Margaret and Benedick talking in a confusing way. The way they toss puns with one another is similar to the way that Benedick would speak to Beatrice in one of their many battles of wit. This could be interpreted to mean that Benedick wants (or has) the same relationship with Margaret as he does with Beatrice.
Margaret's remarks often include sexual innuendos, but I don't think the scene here between Margaret and Benedick suggests that they're attracted to each other as much as it shows Margaret to be a young woman with pretty outspoken attitudes about sex. It's generally the same free-spirited and playful language she uses in her earlier scenes with Balthasar, Hero, and Beatrice.
I believe Margaret is only kidding when she asks Benedick to write a sonnet for her "in praise of her beauty." This is proven when Margaret quickly agrees to fetch Beatrice for Benedick, and most of the rest of Act V, Scene 2 focuses on the developing relationship between Benedick and Beatrice.