Charger SRT 392
2016 srt 392 6.4. Just started not long ago, the car shakes when in park or idle at a red light or any stop. Never happened, now always happened. Car has 130000 kms and still under extended warranty. At first I took to get full fuel system treatment, paid 100 bucks and no results. So took to dealer for warranty service as I identified as issue and they came back with I need to change spark plugs. Didn't feel right about that because manual says 160000 km change of those, and no, I baby the car, little too much, and never track driven or stomped. I also have srt 392 2015 with 132000 kms and this issue does not exist. Any ideas to give me to give a possibly incorrect dealership some clues to look for? Thabks so much for the help!!