I just recently bought an 04 RX-8 with about 130,000 miles. It drives very well and I have no problem with it while driving. The only thing I notice is when I am stopped or in neutral it vibrates heavily in the cabin (where the driver and passenger sit) but when I drive it goes away. Any ideas on how to fix this?

 

Sounds a lot to me like the motor mounts. Does the shifter shake badly while at idle? If so, that is your problem right there. It is a relatively common issue and is easily fixed DIY if you have some skills.

 

Yes the shifter shakes a little more than it should while at a stop or in neutral. Thanks for your help!

 

As Chrishoky suggested, motor mounts indeed :-) just had mine replaced all the vibration disappeared

 

How much did it cost you? I have a rust issue as well and I'm not looking forward to paying the big bucks