ryzen 3 1200 no display

i have ryzen 3 1200 mobo - msi A320m pro vd/s v2 ram - adata 4gb ddr4 2666mhz PSU- 500watts True rated Gpu - Giagabyte RX570 my problem is after few minutes after boot my GPU no Signal then Fans spins louder ,but rgb of GPU's on , mouse and keybord working , VGA light is on ...