Our corgi, Stoli, is about a year and a half old. Recently we have noticed that after a deep sleep he seems like he's stiff or it's hard for him to walk the first couple of steps. After a minute or two he's perfectly fine and ready to go. Is this something we should be concerned about? We've really upped his exercise in the last month. We make sure to jog or walk at least a mile every day. Any ideas?

Thanks for all your help!

(I had to include a picture of our little ham!)