That happens when I try to play a large amp on a small battery/powersupply
The voltage dips so low that the amp literally cuts off.
Check your voltages.
Some reasons for voltage dips could be (in order of most likely to least likely):
1.)Bolts/nuts/screws on power wires not making good contact. Check all of them.
2.) Subs may be wired too low. How are they wired? And can your amp play those ohms?
3.) small power wires (so feel if it's getting hot).
4.) Amp itself has a problem.
5.) Alternator/battery probably going thru. (you'd notice this in your car otherwise though, least likely scenario here)