Question PC is not starting up and Also windows shut down abnormally some times

Sep 12, 2019
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Hi Guys
Sometimes, when i turn my old PC on, I don't see anything on my LCD, but Power Supply and CPU Fan is working.
I should turn off and down for several time until i see BIOS version and then windows starts up.
Also, i may work in windows for hours without problem but suddenly it shut down abnormally and there is nothing in LCD and above problem is made again.

Is my problem related to Power supply or MotherBoard or anything else?
Thank You :)

CPU: Intel Pentium G2130
M/B: Asrock H61-M socket 1155
Power: 350w
HDD: Hitachi 500GB 7200rpm
DVD-RW: Liteon
VGA and Sound: Onboard
RAM: 4GB DDR3 (one Module)