When the car is completely warmed up and the needle is sets in the middle, it goes back down to cold then comes back up halfway and then back down to cold and then back to the middle....then it stops for a lil bit and does it again and again. Does anyone know what the problem might be? There's no check engine light on or anything, and the car SEEMS like its running fine. I'm just scared something is going to happen soon and i wanna fix it before it gets worse.

 

Your coolant temp. sensor is bad. My A4 was doin the exact samething. It's very common on these cars. Just go to your local dealer and pick up a new sensor and put it in. I did it on mine about a month ago and it fixed that problem. There is a pretty good diy on www.a4mods.com