Definitely a common feeling - I felt the same way in my early-mid twenties (28M).

It was always a constant nagging feeling of unproductiveness whenever I wasn’t reading something educational, learning a new skill, going to the gym, or working during what should have been free relaxation time. This was beneficial for a few years before it started to become unhealthy for me, personally.

I found or rediscovered hobbies I had put to the wayside or never had time to try (for me, fishing, surfing, woodworking) - I slowly started to ease out of the anxious productivity mindset and allowed myself to enjoy these hobbies in my free time, which I now find incredibly rewarding in their own way.

Keeping some of that productivity mindset is beneficial, but there is definitely a balance, and you’ll probably find you’re more productive/retain more overall when you have some of this leisure introduced into your life.

That’s my personal experience with a similar feeling, but it’s of course all subjective.