Timid playing with others

Our pup (Copper) is a 15 week old English setter. He is very sweet, doing a great job with training, and seems like an overall happy dog.

We enrolled him in a puppy class and so he’s had some opportunities to play with other dogs there (off leash). However, copper always runs away with his tail tucked whenever other dogs engage with him. He will occasionally reengage with his tail wagging, but after the dogs take interest in him again, he wants to run off and wants to hide behind me.

At this age, does this indicate that he might have fear of other dogs? Or is this a normal way of learning what it’s like to play with others?

For what it’s worth he always wants to approach other dogs in the street. He’s also gone on one walk with a friend’s dog (who truthfully doesn’t love other dogs, especially puppies) and that seemed to go pretty well. Only one time did that other dog correct copper but otherwise they got along fine.