Out of the blue limping

Question
This past Sunday afternoon,  after a nap my cocker Lady got up to walk around and was limping on one leg.   Took her out for her potty break played with her for a bit, and it went away.  Later on that night again she woke up and was limping.  My mother and I checked her leg felt nothing wrong.  Checked her paw saw nothing wrong.  It seems to only happen once she wakes up.  She is 5 1/2 years old and we have been having alot of rain here.  Could it be signs of Arthritis?  And sometimes it looks like it could be both legs.

Answer
Was it a front leg or a back leg?  How badly was she limping?  Is she a very active dog?

I know you checked her paw, but feel her entire leg & hip joint gently and then gently & gradually increase the pressure and bend her leg to see if there's a particular spot that's hurting her.

At her age it's certainly time to get her on a glucosamine supplement like Cosequin anyway.  But it's very possible she's just bruised or strained a leg jumping off or onto something.
Delores