Benz ml 550 2009...won’t start?

Question

The dashboard does not light up when u open the door. There is a continuous beeping noise that is coming out of the car even though it is completely off and won’t start. The only thing that lights up is the words mph and miles on the speedometers. When I put the key in it will not start at all. Was working perfectly fine yesterday. Pls help as soon as you can and thanks in advance!!!