it could have not been done when you racked it and you simply just recirculated the yeast and they are continuing again.
or it could just be the release of gases as atchinator stated. Are you dry hopping in secondary? Sometimes the hops create nucleation points and c02 is released when dry hopping.
Who knows, only way to check is with your hydrometer. 3 days stable, then you can rack.
EDIT: just saw your OG. Depends on what yeast you are using, but yeah most likely its getting a bit tired of doing what its doing.