Static noise on display, how to diagnose the cause?

About twice a month when I open my laptop there is noise on the LCD screen. Some pixels here and there just light up in random colors. Intensity vary, sometimes there is lot of them, some time there is only a few. Shuting down or putting the laptop to sleep and starting again fix the issue.

I opened the laptop and did a visual inspection and couldn't find anything wrong. How can I find what is causing the issue?

Thanks