<human>: Can you summarize the given text in a few sentences?

Hey everybody,

I just recently started running to prevent my little thesis gut of developing into a belly. To that end, I bought some decent running shoes and started following a [Couch-to-5K] programme, including their [suggested stretches] I've just finished the third week, but I'm starting to notice some soreness in my knees - no real pain, just the past few days it's been noticeable. Is this something I should be concerned about nipping in the bud, or is this common starting out? Is there anything I might be doing wrong starting out?

Thanks for any help or advice you can give!
<bot>: Starting runner, normal weight, starting to notice some knee-aches. Is this a sign of a problem, or normal stuff?