IMHO, you've got a leaky seal on/in your Torque Converter AND/OR you need to have your tranny fluid changed & the internal filter screen replaced.
Another possibility (less likely) that may be discussed is an internal pump/pump seal problem, but that would be an issue whenever you come to idle & your tranny would eventually burn up from lack of fluid circulation.
Your ATF probably looks/smells OK, you just get the low pressure kick. I've got that to a smaller degree in my Contour & here is what I have done. I added a little more fluid - 'bout 1/2 quart until I gather the time to pull the tranny & replace the filter, TC, & add a shift kit.
For now the symptom is almost gone, I just know that at one point I will need to replace the filter & TC. If you have the know-how to pull the engine from your car, you can probably perform the work yourself. Its really not very complicated once you get it out of the car.
