Dog walks in "U-Shape"?

[OreoJ]

Hi, i'm new to this site, but anyway I would like to ask a question-

My Minniature Rat Terrier is probably the weirdest dog you will ever meet, and he does this really weird thing that I never see in other dogs-

When he gets excited or nervous he tends go into a U-shape. Then he actually walks foreward (still in the U-shape) and then does normal dog things (goes in submissive pose, wags his tail, ect.)

So, does anyone know what this is? I'm stumped.