Behringer NU6000

[coax]

Hi Guys,
I am seeking you all help with a Behringer NU6000 power amplifier. The problem it will power up fan start turning three minutes later it will shut off and fifteen seconds later it power back up and that cycle will continue as long as you leave it on.
I check all the joints for cold solder but all is in good contact, this unit is brand new but the warranty is out so I will appreciate all the help from you all
to get this amp working

Cheers Guys
Coax