I think this was a made-for-tv movie. In English, color. Likely from the 90s.

There are crimes happening, and we keep seeing the front of a car (maybe the back, though–it has been a while) and it had a whole row of lights along/above the bumper in addition to the headlights. It seems like the mysterious vehicle was often partially hidden by fog. At the time I was thinking there couldn’t be many cars with lights like that, so why couldn’t the characters figure out or narrow down who the (killer? stalker?) person was.
Towards the end of the movie, we find out the car belongs to “the woman’s mother-in-law,” so the movie probably has a female protagonist, but I can’t remember any of the characters!
Hopefully someone else remembers this distinctive car and can help out. Thanks.