I currently have a gray g35 coupe and I have a few problems.
1. The passenger side window won't work sometimes. On and off problem..works most of the times but somtimes it won't go down. Could it be the switch?

2. The left side speakers have the same problem. It goes on n off continuously and I heard it may be the built-in amp from the factory deck!

 

you can either take the window motors apart and clean it or have them replaced if you are still under warranty... there is a diy here, just search for it... common problem for g35's