1998 Ford F-150 Running Rough After Start-up

I have a 1998 Ford F-150 with the 4.2 litre V6 with about 160K miles. When it is about 40 degrees F ambient temp or colder, when I start the vehicle after it has been idle for 8-12 hours, the vehicle at times starts and runs very rough. The vehicle runs so rough that I fear that it will stall and be unable to be driven. However I baby the vehicle up to speed and then after 1-2 minutes of operation at speed or 1 mile or so, the vehicle returns to normal smooth operation. Sometimes the motor will die as soon as I start it and when I recrank the motor, the starter drags when I try to restart. The vehicle doesn't always do this. About 1/2 the time the vehicle starts and runs perfectly and the other 1/2 the time it runs very rough as described above. When the vehicle operates roughly, I do not get a check engine light. It acts like a engine sensor is malfunctioning but without a trouble code, I don't know where to turn. I appreciate any help you may be able to give me. Thanks in advance.