07 sport trac

I have an 07 Sport Trac with the 4.6 V8, occasionally when I start the truck, the message center will display "passanger door open" then flips to "chk rr turn lamp" then flips to "chk lr turn lamp" This continues back and forth until the car is turned off. When this happens, the turn signals work but flash very fast. If you stop while it flips to the passenger door open the interior dome light turns on until you start moving again. I have called the ford service department, but since it does not do it every time you start the car, they don't know what's wrong because it won't do it when I take it in. The service department has no idea what is causing this or how to fix it. My fear is that my lights will stop working all together and won't have them at night and get in an accident. This has happen 4 times in the last two weeks, and had not happen since last March. I bought the truck in January of 08. Happen the first time in Febraury, two or three days in a row when I left work. Then again about 4 weeks later in March then not once until the end of October. I called and made an appointment with Ford for the second week in November and it did not do it agian until the end of November, then 6-8 times in December-March then not again until two weeks ago. It seems to have something to do with cold weather as it never happens in the summer. If anyone has any idea about what may be causing this problem or how to fix it, help would be appreciated. It is still under warranty for another 9000 miles, and would like it taken care of before the warranty expires.