You can only test it by taking it out and sticking a different graphics card in, any card will do that you know is in working order.
if your system boots okay, your original card is faulty.
Alternatively, you could put your card in to a different computer to see if it causes the same boot problem.
However, a faulty graphics card should trigger a series of error beeps at boot time, so if you aren't getting those beeps it's unlikely to be the graphics card.
There are many causes of a "boot loop" but all are related to hardware. That's the purpose of the BIOS beeps, they assist in you in identifying which component is causing the problem.