im starting to have this problem where when i start my car it starts fine..and then the car kinda sounds funny and it shakes..just when im idle..and i put it in drive (auto) and it still shakes as it moves forward...and shakes if im in reverse..and after i finally take off..itll go away..and wont really happen anymore for that day..usually happens in the mornings..but it happened last night right when i was pulling in it started shaking...anyone has this problem? or anyone have this idea? oh and after i got the car back from the nissan dealer i have a new "nissan battery" a friend of mine told me that its probably just a battery that got charged and they slapped that sticker on there

Is your car at the correct idle speed? When warmed up the engine should idle at around 750 RPM.

im pretty sure its the muffler...eh cuz now when it happens (only happens sometimes) when i give it gas..it spurs out like a machine gun and sounds horrible..and then like 2 minutes later it doesnt shake and sounds normal