Why not running after stop

What is your question?

I have a 2012 Chevrolet Tahoe with a problem in the transmission that when you turn it on and put it in gear it works very well but if you stop like for example in a traffic light and then it will continue the march it stays in neutral and does not move So I proceed to turn off the engine and turn it on again and then I can continue the march but if I stop it does not want to move again and I have to go through the same process of turning it off and on again to continue its march.