Yukon15

I think I've been having the same problem that you described with my 2015 Yukon but mine is an SLT. Every time I was idle the car would start to shake/shiver. I've taken it in to service a total of 3 times for this issue and each time they said it was an engine mount issue. This last time, they told me that one of my engine mounts was actually installed backwards and they replaced my engine mounts with new parts just in case. If I'm being nitpicky, I still feel a very very subtle vibration but I think that may be normal vibrations at this point. I had posted this issue somewhere else and someone mentioned checking to see if your plugs are loose? I'm not sure what plugs exactly though. HOWEVER, now that it's warmed up here in Texas and I've had to crank up the AC the shivering during Idle has returned but only when I have the AC on really high. I guess it's time to head back into service. I am honestly one more problem away from trading this Yukon in for the Expedition.