16 Month Staring

My son is 16 months old and has been hitting all milestone on time, if not early. That is, with the exception of social development. He often stares intensely at other adults or children when in public. For example, this evening we took him to a park and he would go up to other children and just stare at them but wouldn’t try and play? When we’re talking staring, I mean like making intense eye contact to the point where I’ve been asked by other kids “why is he staring at me?”. He certainly likes to observe others from a distance and then when they leave the area, takes over what they were doing. Like he is learning how to do different things from them? I don’t know. Again, all other areas of development are on track or even advanced. He can do pretty complex puzzles for his age, he is speaking several words, and his receptive language is pretty advanced as well. Wondering if anyone has had a similar experience to this with their children or if they’ve experienced this as a child themselves? I’ve mentioned autism to my pediatrician and he didn’t take it too seriously but something in my gut is telling me something is off. Any advice is greatly appreciated!