Partial pictures at start up

When I turn on my tv first time in the morning, the picture loads slowly and often with a very small picture in the upper left corner. I have tried resizing through the tv menu, which doesn't work. I am able to fix it via the cable box video display menu by resetting picture to 4:3 then back to 16:9 hd. Once the picture is resized, which sometimes happens automatically, the system seems to work fine for the rest of the day. I have run system refresh and turned off zoom on both the box and tv. What's going on?