CPU fan not stoping after shutdown and start up problems!!!

[Rhodes]

Recently my Pc come up with a odd behaviour. Can not startup unless I turn off my PSU.
I hit the power button, the leds and fans start up but everything goes off. Then they do the same thing over and over.

Only way to switch on the computer is to turn off the PSU, wait a little and then every thing runs fine. PC star up, windows loads and works fine.

If I shutdown for like 2/2:30 hours, I can turn it on fine. If more, like 8h (from one day to the other day), the problem exist.

And yesterday after I shutdown I decided to take a look and I found out that my cpu fan does not stop spinning.

GPU,PSU and case fans stop, the CPU one not, unless the PSU is turn off (lovely).


I recently did some upgrade to my PC, put a SSD for OS and programs, My old HHD for data storage, more memory-12 gb ddr3 and 64bit OS - Windows 7.

All was well, SH3 with the heavy mods that i couldn't run before.

The only change I did recently (3 weeks ago) was getting a new GPU. My old Geforce 9800 GT was basically one jet engine, the sound of the fan was loud. After doing some research, I got a geforce gtx 1050.

My doubts were a 730 with a passive sink, and I think, even with 2gb ddr3 was inferior to my old card or a gpu with a active sink but a silent one.



My board as only pci express 2.0 16x, the new gpu is a 3.0 - can this be the cause of all the problems?

The situation I am telling here, just arouse 2 weeks after I had installed the new graphic card.
Did my PSU may need to be replaced since it is old and possible becoming faulty?

Any thoughts, advices?



Spcs
Mobo - Asus P755D-E deluxe
CPU - Intel I5
GPU - asus nvidia geforce gtx 1050 2gb dd5
Ram - 12 gb Kingston (one is hyper fury)