Question weird sudden shut downs

May 18, 2020

first of all this is my pc specs
Asus b450-f
G.skill 2x8 16gb 3200mhz
asus dual 2060 super
barracuda 2tb
hp 900 m.2 nvme 250gb
Evga bronze B5 650watt

i had it for nearly 6 months it was working great ( excpet for bluesceens that i got nearly 5 times since i got my pc ), but this morning i woke up and turned on my pc to study after 3 hours it shut down by itself. i tried to turn it on again but nothing happend after i plugged away the cable from electricity and plugged it in again , it turned on it and got into windows then lasted nearly 5 min then shuts down again.

i tried another powersupply G2 850 watt from evga same thing turns on for a few mins then shuts down
also i tried to change the cable that connects to electricity same story.

is the problem from the motherboard or what?
can anyone help me?