According to your description, you may suffer from a condition known as night blindness. People who suffers from night blindness see poorly in darkness or dim light. But they can see it clearly daytime or somewhere have adequate amounts of light. In some cases, night blindness is a symptom of a serious underlying condition. Night blindness is often the first symptom of a cataract. Besides, they may also caused by lacks Vitamin A. So, you may eat more food contains of Vitamin A.
It is quite normal. Some people find their vision really bad at night even though there's nothing wrong with their eyes. That's because the pupils open wider at night to allow more light to get into the eyes. Thus the eyes cannot focus easily, which cause the vision problem at night. If you can hardly see anything at night, you'd better go to see a doctor to have your eyes checked because some people who have difficult seeing at night may suffer night blindness.
Many factors should be taken into account, I think, such as your age, your actual vision and your working hours. First, it may be a normal reflect of eye fatigue or worseness of your vision, so you should have enough break when feeling blurred or you may have an eye exam. Another possibility should be that you may turn into night blindness thus you need to see a doctor.