Dell Inspiron e1505 display problems

Hi I am having a little issue here with my labtop for a couple days now.I can't accurately determine the intervals it occurs but it is after prolonged use like 18-24 hours or so the screen kinda rocks from side 2 side violently.....The only way to stop it is if i take the mouse pointer and put it like under the taskbar of the screen then it stops,but if i move my mouse cursor back then it starts and I am not able to click anything on the screen cause it doesn't flicker like from black to light it just dances side to side really fast.But after I reboot it takes like 16 hours before the problem starts back.I did a complete reinstall of my windows and it still happens so i am sure it isn't a virus or spyware.The only external device connected to it is a usb mouse I use.I even tried the diagnostics all the tests past flawlessly I tried using it without the external mouse but it still persists.Could you guys determine what may be causing this?