Answer:
He feels anxious about aging.
Step-by-step explanation:
What appears to be causing the speaker in the excerpt to pay so much attention to his own appearance is public attention; he thinks about the criticism others might make by watching him from afar.
This criticism, at the same time, causes him to ponder about time and the effects it has on his image, which is evidenced with his comment about "a bold spot" in the middle of his hair and his "thin arms and legs".