I have a 2008 lmm with 65000 miles on it. In the past week I've noticed the motor shakes when I turn it off. I can feel it in the cab. My last truck was a 06 lbz and it shaked a lot but that was like it for the 3 years I owned it. But with my truck now it just stated to. The other day it smelled like my serpentine belt was getting a little hot and I don't know if that has something to do with it too. Can someone help me out. Thanks.