How to tell if a young child has developmental or persistent stuttering?

How to tell if a young child has developmental or persistent stuttering? Looking for advice. My 2.5 year old son has been stuttering for about 4 months. It began as stuttering on the first syllable of a sentence, sometimes getting stuck for 5-15 seconds, one time I swear a solid 45 seconds to a minute in the grocery store. It can also be elongated sounds. It almost completely stopped for a couple weeks until last week, the syllables again and since yesterday this gasping for air at the beginning of sentences. The instances in the video are mild, it is typically much more pronounced. I’m concerned. I’m adopted so unsure of family history. my partner has no history in his family. How am I meant to know if this is developmental or clinical? What should we do? Thank you.