The terms “essential/nonessential” NEVER apply to a prepositional phrase. Prepositional phrases that are adjectives tend to be right after the word they modify; prepositional phrases that are adverbs can float around in the sentence. One prepositional phrase that just modifies rarely has punctuation.
…The man in the red shirt is my dad.
…The car near mine was also damaged.
…We listened to his speech for an hour.
…Did you see him at the stadium at any time?