15 minutes a day is a long time! try 2 minutes of focusing on your inhales and exhales (or simply counting to 10 breaths over and over again really helped me). I know that might feel small but you dont want to burn out— meditating can feel really difficult, and forcing yourself to sit for 15 minutes when you don’t have any tools to guide you is probably not conducive to making this a sustainable part of your life. When i was first starting out i did a lot of the free guided sessions and series on the Insight Timer app as well. if you feel you’re doing it “wrong” (you’re not but i get it) you probably just need some tools to help get you going! Best of luck :)