Hi Sandro,
This issue usually cause due to VGA cable issues. I would suggest you to try using a different cable and check if it works for you.
You may also try updating Video card drivers and check if it helps.
Update a driver for hardware that isn't working properly:
If updating the drivers and using a different cable did not help, then it would be better to contact the computer or graphics card manufacturer for further assistance with this issue.
Please feel free to visit our website for any help with Windows Operating System.