I wouldn't be worried about the .14V less. Not a big deal as long as you are near 12V.
Almost sounds like something is heating up and messing up. Meaning the heat or expansion of something. Maybe a wire etc.
Try starting the car and wiggling the various wire harnesses to see if one has a break and maybe the only time it is making contact is when it's cold.
Read up on your ignition circuit. Primarily how it starts. In the 96-03's I have read it and know that the ICM controls nearly everything for the first 10 seconds, then it hands things off to the pcm. If that's the same in your case, you should see spark in the first 10 seconds automatically unless the icm/crank/cam sensors or wiring to them is having anissue.
