I've been searching google and forums and maybe I'm just using bad search terms or something but I'm not coming up with a lot of helpful information so figured I'd just make a thread and ask.

I have a couple things going on. First thing, occasionally my 04 G35 AT will be driving fine but when I stop at a light all of a sudden it will have no power when trying to move again and if I shift it myself it will go to 3rd gear and not have any change in rpm's while upshifting. It feels like trying to start from a dead stop in 3rd gear in a manual and it drives fine once you get up to that point but it wont have power again in first or second until I turn the car off and back on. Sometimes this happens once while driving and another time I've had it happen at every single stop light and stop sign. It also started happening when it was cold out and when it's hot out so I'm not entirely sure what is going on. This is my first automatic so I'm very unfamiliar with how these transmissions work.

Now the second issue, not sure if this is transmission related or not but it feels like that's where it's coming from. When I start the car there is a loud hum that I can't pinpoint a location and a vibration that seems to be coming from under the car where the transmission is. As soon as I give it some throttle it goes away but if I let off the throttle at all it will come back. Usually the noise and vibration become quieter after a few minutes but at first it is pretty loud. It hasn't felt like it is affecting the performance and the transmission seems to shift fine but it still bugs me. I don't like overlooking things just because they aren't causing major problems.

Hopefully someone can help me out and thanks in advance.