Question Graphics card producing Solid color at Random times?

Oct 19, 2020
Recently I upgraded my motherboard to Gigabyte B75 M-S from Asus H61M-K motherboard in my PC. It was running fine for 1 week. After one week it produced a solid color display while watching videos in Youtube. Then I restarted the PC. Within 10mins again it produced a solid color display where the sound also either got stucks or won't. I thought it was a graphic card issue. I was using a GTX1060 3gb . Then I starting diagnosing my PC. But after some attempts it gave a black screen when restarting (that too after 15 seconds of Power On).
I tried these steps.
Reinstalling the NVIDIA drivers.
Resetting the BIOS
Updated my BIOS(but only one version is available for my Motherboard).
Cleaning the RAM and Running with single Stick and with different slot
Cleaned My Processor
Operated my motherboard outside with only graphics card

When trying the above things either it produced a solid color display at random times (Time varies) when it is idle or when playing games or watching Youtube Videos.
The only message I got after restarting is "Application has blocked from accessing Graphics Hardware".
After 2 days I tried with running with onboard VGA. Then it was working fine without any crashes.
I thought it was the Graphics card. But one day it was working fine even after continous 2 hrs of heavy Gaming. My GPU temp. was also within 50 - 55 C.

Then I started noticing my PSU. It is a 550w Thermaltake PSU ,about 10yrs old.
Then one day I found that the wifi dongle which was inserted to the back of my motherboard sometimes doesn't detect WIFI even if WIFI is proper.
Also during Gaming my Joystick disconnects sometimes.
These problems occurred when my motherboard is connected to the graphics card.
But without Graphics card everything works fine without any issues.
Now I think it was my PSU, since it was very old.

But still I'm not confirm about it. Any ideas regarding my issue ? Is it really my PSU or Motherboard Compatibility with my Graphics card.