That the eyes blink when exposed to bright light is called blink reflex which is a safety mechanism of human eyes. This mechanism usually can save our eyes from damages or foreign irritation. If you suddenly enter a bright environment or a beam of intense light directly points at you, your eyes cannot immediately adjusted to the bright light. The amount of light that enter your eyes is controlled by the pupils. Since the speed of the light to your eyes is higher than that of blinking eyes, your pupils cannot close completely thus there is too much light getting in your eyes. Compensation is made by blinking eyes to cut of the excessive light. Besides bright light, your eyes can also blink as the reaction to loud sound.
Yeah, I think it is normal that people cannot help blinking eyes when exposed to bright light suddenly. Last week, I went to watch a movie with my friends in a cinema, when I walked outside from the dark cinema after the movie was over, I also blinked more than usual. After a while, I adjusted to the bright light. Therefore, I do not think it abnormal. But if you blink frequently even when you are not exposed to the bright light in a sudden, you should check out whether you are catching a cold or suffering from a sinus infection. Even a bit of dirty things can stimulate our ocular nerve and result in the pain in the eye, hence blinking more. In this case, you should go to hospital and consult an experienced eye doctor so that you can receive a prompt treatment.