Yes, it sounds like Ra to me.  Especially before you get on some treatment, you will find that sitting in one position for even 15 minutes can make you stiff! So, try and shift positions often, stand up now and then (and don't be ashamed to explain why.  I heard someone explain that to a group I was in, a couple of years before I got diagnosed, and later I understood why, and how she felt!)

Also, you noticed that you started to loosen up after a few steps, a few minutes.  This is something to remember - that you can help yourself by trying to stay active, even if it's difficult at first.  You don't want to push it to extremes, that will backfire, but you can explore the limits of how much is good, and how much is too much.  And this may go thorugh cycles too.  Are you on any kind of anti-inflammatory meds yet?  Sometimes doctors will suggest over the counter meds like Ibuprofen or Aleve for the time being, until you get to a rheumatologist.