I removed my gpu to test if the problem was solved and then this happened. with gpu the screen freezes but don't show the white squares in the picture.
Have you tried the other PCIE slot for your GPU on your motherboard? It probably will cause the same issue but it's still worth a try. Also try using one stick of RAM and boot up the system of you have a dual-kit RAM. Rinse and repeat for the other stick of RAM. If that does not fix the issue then there is more concerning problem.
There could be 3 issues that we are dealing in here - PSU, motherboard and CPU. I still don't know what the make and model of your PSU is, so I can't really comment on that aside from the unit probably giving out from degradation, hence being defective...