He comes with excuses. His reaction shows his hesitance. He asks, who am I? meaning: I am not capable of doing this. Forty years ago, he was eager to fight for Israel, now he has his doubts. Moses was a humble man. Numbers 12:3 reads, Now the man Moses was very meek, more than all people who were on the face of the earth.
His humbleness is shown here. But humbleness is no excuse to refuse a command of God.
11 But Moses said to God, “Who am I that I should go to Pharaoh and bring the children of Israel out of Egypt?”