Thanks for all the suggestions guys. I'll definitely look into the motor mount issue. I was unaware that the engine mounts had this dynamic function. That would definitely explain the problem if the mounts weren't switching to the soft mode. Is the function of the mounts detectable with a OBD computer plug in module? I also was initially suspicious that maybe the cold weather around here was partly or mostly to blame but it doesn't seem to matter much between 6 degF and 35 degF (the range around here the past 3-4 months).