There are many speculations as to why this fear is resurfacing now. One may be as a result of some event that you have been exposed to whether by the media or an event you had heard of and kept in your subconsciousness that is now coming to light. Another possibility is coming to the realization of one's own mortality.
It is also possible to be experiencing general anxiety which you may be noticing more in yourself while he is driving and trying to associate it with the driving instead of attribute it to something else.
What may be helpful is to journal down some emotions and thoughts that come to mind when you experience this feeling. Try to notice if there are other times in the day when you feel the same (anxiety has many physiological responses such as changes in breathing, heart rate, perspiration, dilation of pupils etc) If you notice these, deep abdominal breathing can help. Other options are medications or herbal supplements if you feel that it is more of a panic attack you have that is too much to handle. If it is not at all times as you've explained, then try to see if the feelings decrease with time or get worse.
I forgot to mention that I do not experience this "fear" when riding with others. Does that make a difference in anything you are suggesting...such as it being situational? Also, I don't think I can journal during the drive, because I'm too terrified to look down. But, I have wondered about going into the back seat. Maybe, even as crazy as this sounds, blind folding myself!