What does this odd reaction suggest about Gregor in "The Metamorphosis"?
When Gregor wakes to discover he has become a gigantic insect, he is mostly intent on the practical implications of his metamorphosis - how to get out of bed, how to get to his job, and so on. He never wonders why or how he has changed.
Gregor does begin by contemplating what has happened to him when he first becomes aware of his transformation, however, you are right in identifying that his concerns quickly switch to more practical matters. I think one of the reasons why this is is because Kafka is presenting us with a man who has been worn down by the work he is doing. He is literally treated like a cockroach by his work and society at large, and the way that he is not able to contemplate these bigger questions suggests the way that his work completely dominates and possesses him. One of his first thoughts after he has become aware of how he has changed is how terrible his work is:
"Oh, God," he thought, "what a strenuous profession I've picked! Day in day out on the road. It's a lot more stressful than the work in the home office, and along with everything else I also have to put up with these agonies of traveling--worrying about making trains, having bad, irregular meals, meeting new people all the time, but never forming any lasting friendships that mellow into anything intimate."
His transformation, then, perhaps allows him to voice his feelings and anger at his state of life, making him realise how much of a metaphorical bug he has been, if not a literal one. Thus Kafka, by making Gregor deliberately not ask these bigger questions, is drawing attention to the way in which we are all, to a greater or lesser extent, treated like bugs in our work and by society at large.