yeah, sound like there is something intermittently wrong with your one.
When i turn mine on, it always takes ~1.5 seconds to get to the rigol logo screen.
For about half a second before that i get some random horizontal lines on the screen, then the rigol logo appears.
Sometimes, if i turn it off then on again soon, the random lines are replaced by the previous image that was on the screen before i switched if off. So i think the lines/afterimage is just whatever is in video memory when its powered on.