For me -
It's the ads loading!
Site opens up with the 'ad' space at the top blank, followed by the list of posts.
Ad then loads in the open space at the top of the page
and then the page goes crazy, sometimes jumping all the way to the bottom.
It does the shifting thing occasionally.
(I think there is something in the ad contents that causes a 'page down' or other strange things.)
Brother Mike - 2012 GW w/MotorTrike Razor