New GPU but no signal to monitor and system keeps restarting..Need help

[Captainblackops]

Guys,
Today i installed a new Rx480 and when i switched on the PC there is no signal to monitor and after a while it keeps restarting! Now i removed my GPU and connected monitor to mobo output but when i switched on there is no signal and system keeps restarting with a gap of 10 seconds !! Kindly help me out here

Specs;
Mobo - Gigabyte B150m D3H
CPU - Core i5
PSU - Seasonic s12ii 620w

 

[Captainblackops]

MERGED QUESTION
Question from Captainblackops : "New GPU but no signal to monitor and system keeps restarting..Need help"

Guys,
Today i installed a new Rx480 and when i switched on the PC there is no signal to monitor and after a while it keeps restarting! Now i removed my GPU and connected monitor to mobo output but when i switched on there is stillno signal and system keeps restarting with a gap of 10 seconds !! Kindly help me out here

Note: It is brand new PC and working fine for past 1 week till today when i installed new GPU
Specs;
Mobo - Gigabyte B150m D3H
CPU - Core i5
PSU - Seasonic s12ii 620w