driver heats up

Dear Sir I am using Arduino UNO R3 and L298N Bridge for running stepper motor of 1.8deg. 12v 2.8A. I have given 12v external power supply but within 10 to 15 sec L298N board gets heatup and motor stop for 12 sec and again it starts and stop So please tell us Why its happening and also guide us for proper solution.

Dear Sir I am using Arduino UNO R3 and L298N Bridge for running stepper motor of 1.8deg. 12v 2.8A. I have given 12v external power supply but within 10 to 15 sec L298N board gets heatup and motor stop for 12 sec and again it starts and stop So please tell us Why its happening and also guide us for proper solution.