I would say 80-90% of the time the car has an overall vibration that does not affect the performance but you can feel it while driving and a little less when in idle. Every once in a while the vibration will go away for a little while and the car feels smooth as if it was bran new. This doesn't last long before the vibration comes back. I've had the mounts, brakes, checked and even have since put on new tires. Again, it doesn't affect the performance but is there most of the time.
Any ideas?
No ideas, lots of questions.
You're going to need to provide considerably more information to get any kind of useful response.
Engine, mileage, transmission, speed for vibration and anything else that you notice and when.
I have 85,000 miles. Its a 6 speed manual transmission. 2.0 liter. It occurs as soon as the car starts and happens at idle and at all speeds.
What you have sounds like a rough running engine, there is a tech bulletin out for this engine running rough due to carbon buildup and you are well into the mileage range for this to occur. Good news is you can probably fix this yourself for about $20.
Clean your throttle body and clean your valves. Google up direct inject valve and throttle body cleaning, watch some utubes on how to do this and pick the method that you know you can do.
Big change your bottom guide rail of the balancer chain is broken, or that the balance chain tensioner is broken. Very common for the B207 and its GM counterparts.
because with the broken balance guide rail or chain tensioner, you will have enough slack on the balancing chain that it sometimes jumps. Therefore often the balancers are in the incorrect position and the engine is vibrating heavily because it is out of balance, but sometimes the chain jumps and the balancers are in the proper position again causing a smooth running engine.