I have a 2006 CTS. Recently while driving, the car is running at high rpm's and does not seem to want to switch gears. Then after coming to a stop it seems like the car switches into neutral. Now after not being run in a few days, when cranked the entire car shakes. I don't know if it's a gear, clutch, sensor, etc. issue. Please help. Thanks.

 

Obviously something is not right. Definitely sounds like a trans problem, but you really need to have it scanned for codes to see what might be amiss. You will likely need to take it to a shop for repairs, regardless. Really need more info...