Ok, I couldn't stand it so I just went outside and tried to start my XF. As I suspected, STARTED RIGHT UP! This is why I really hesitate having it towed to a dealer the next time it doesn't start because, by the time I get it there, it will start and they won't be able to diagnose what's wrong. I may just have to take it in and let them try to start it for a week or two until it happens at their place. I believe it has to do with the security system (SKREEM?) but the manual said that codes are stored if there is any problems with this unit and no codes appear. Either this is a complicated issue that is hard to diagnose or it's something as simple as needing a new battery, which I hope the dealer would have checked first. Since mine's an '04 maybe I'll just replace the battery since I will have to do it one day anyway and see if it still has starting issues.