False starts in the morning

Why is it true that everytime I place the collar around the dog and step into the darkness of the early morning to allow him to make his morning deposit, that he will inevitably do something like stop dead in his tracks somewhere in the darkness of the carport for no apparent reason? When that happens, I usually stumble over him or suddenly pull to a halt in trying to step through the darkness out to the front yard. This morning, I got up and asked Tex if he wanted to go outside. He jumped down to the floor and walked over to the mud room to wait for me to place his collar around his neck, then he moved over too the door to wait for me to open the door. Then I opened the door and he stepped into the darkness of the carport. As he trotted around the car in the carport and started heading out toward the grass, he suddenly stopped dead in his tracks. At that point, I tripped over his body, hunching down on the cold concrete of the carport. I still don't know what caused him to decide to stop there on the concrete. At that point, I had to pull on his leash to get him out of the carport and then pull him further onto the grass. Sometimes what goes on in his brain is hard to fathom.