While you are reading this blog, check in with your body. Can you engage any one muscle on command?
Try tensing your bicep, then your glute muscles one at a time. How about your triceps or calf muscles? Are some easier for you to engage than others? Which ones? Can you pull your navel to your spine?
When you contract a certain muscles do others engage with it or can you isolate it?
Practice for a bit. Engaging some muscles on command can be as challenging as raising an eyebrow or wiggling your ears. Over the next couple weeks when you find yourself waiting for something try to isolate any muscle of your choice and contract it.