Is he happily wide awake? Can be put himself back to sleep?

.. ours did that too at that age. After a lot of shifting, caping naps etc. etc. I just realized that she wanted to do this and was fine doing it. We did eventually drop all feeds at 7-8 months, night sleep consolidated and she doesn't wake up to play anymore but at the time I had to just leave her be.

She would coo and ahh and occasionally emit a scream of annoyance but no sad crying so I stopped thinking about it as a problem.

I think for some kids it seems to be developmental - you can try capping naps to 2.5hrs (seems to be what everyone suggests) but it's a bit of a toss up as to whether or not it'll work.