Try running more x country on dirt before hitting the pavement, for a couple weeks at least. Every couple of years I'll go a few months span where I'll start running again and my knees get a little MEH when I first start up again. Stay on dirt for a bit or final a local high school/college track that has a rubber surface.

Keep those knees up when you run too. Get those upper parts of your leg paralell to the ground when you're running. I ran X country in high school and we did TONS of form running exercises to force outselves to have good habits when running

I ran for a a bit in my mid twenties too and did a half marathon (took about 10 months to get in shape). When I first started up I was so out of shape but I was lucky I was in a remote area at the time with lots of hills and open grassy/dirty areas