Why does my amp keep shorting out?!

Why does my amp keep shorting out?

I bought a Behringer Ultrabass BXL900 90W 1x12" Bass Combo amp along with a Yamaha RBX170 Electric Bass at Guitar Center today, along with a Monster 21' bass amp/guitar cable.

I practiced for about 2 and a half hours after I brought it home and set it up, then it just started making this "boom boom" sound and the power on the amp kept on going out, and when I turned it off, it made another "boom boom" sound and I could turn it on, and after that I could play for maybe 5-10 seconds, then the sound would pop out again and the power would go out and it keeps on repeating.

What should I do and why is it shorting out?

1 month ago
As I said, I bought it today.. I'm pretty sure that it shouldn't have problems already.

I know and I've checked (countless times) if anything's loose, and nothing is. It just goes out of power and it's really irritating when I'm trying to practice.

Connections could be loose, something could be fried... time for a new one!!!