Question Monitor or PC at fault?

Jul 19, 2020
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My 4 year old monitor is acting strangely; sometimes when I boot up the PC, there are horizontal lines on the top left side corner of the screen, but they disappear after a few minutes. As of a few days, I have to restart my PC multiple times in order to get the Windows 10 starting screen. The BIOS/UEFI screen always shows. Strangely, when I put the monitor off and back on when the Windows 10 starting screen does not show, the Windows 10 starting screen does show, but the screen starts flickering and showing strange squares. What is going wrong here?

CPU: AMD Ryzen 3600
GPU: Nvidia GTX 1070