Question 4pin not delivering enough power?

Dec 31, 2019
So lately i bought Ryzen 5 3600, AsRock b450m steel legend and one stick of ddr4 8 gb 3200mhz ram from kingston. I didn't have enough money to afford a whole new pc so i decided to buy theese parts and upgrade in near future (the gpu i have is nvidia's old gt 740) and the problem is that AsRock's MB requires 8 pin but my PSU has 4 pin i red that its possible to run a pc like that but the problem is that its shuts itself down and boots again and again... So i have a question is 350W PSU not enough to power this setup or its something with a board that it won't run unless its plugged to 8 pin connector, or what it could be that im doing wrong.