This movie might be early to late 2000’s, but I’m not too sure. I don’t remember much. There’s a redhead woman and a man, and the man is a killer. She somehow ends up with him and they drive around and I think go to a hotel somewhere in the desert. She looks in the guys trunk and I believe there was a dead person in there. The guy ends up killing the woman, maybe with a shovel and puts her in the trunk. It’s not much, but it may help.
It might be Sombre (1998). The premise is similar, but since I haven’t seen it, I can’t tell if it has the ending you’re describing…
http://www.imdb.com/title/tt0166808/
I don’t remember the name, but could it be the b-movie, where a man marries a hooker or something, and they are driving through the desert on a sort of honeymoon. They accidently run over a man and in the end yoou find out that the man they ran over is actually the man who ran him over… Bad description, I know, but it is starting to annoy me as well 😛
This one, Dark Country
http://www.imdb.com/title/tt0469318/?ref_=nv_sr_1