Learn Italian: Lo inizio a incartare, o vuole anche del pecorino stagionato? - I'll start wrapping it, or do you also want some aged pecorino?

In Italian, del is the partitive article (formed by di + il), used here to express "some" of an uncountable quantity. While you can sometimes drop it, using the partitive article is much more natural and common when offering an unspecified amount of a food item like pecorino.

Why is the pronoun lo at the beginning of the sentence? Doesn't it belong with incartare?

You have two choices here! You can attach it to the infinitive (inizio a incartarlo) or put it before the conjugated verb (lo inizio a incartare). This happens because verbs that describe the phase of an action (like starting, continuing, or finishing) allow the pronoun to "climb" to the front, just like modal verbs do.

Who is the subject of vuole in this context?

The subject is the formal "you" (Lei). This sentence describes a classic shopkeeper-to-customer interaction. The shopkeeper is being polite by using the third-person formal conjugation vuole instead of the informal vuoi.

Why is there an a after inizio?