If is a display problem you can check my running the diag from the boot mean. Turn on the computer. When the DELL™ logo appears, press immediately. Select Diagnostics from the boot menu and press .
Turn the computer on and when the DELL logo appears press F12
this will get you into Diagnostics where you can test the display. If it is a malware problem it will go way while in diagnostics, if it is a hardware problem it will stay.