Is the car running ok? If yes and its only the vibration that's an issue most likely cause is motor mount(s)
spark plug gap Can also be a vacuum leak.
A clogged muffler can.
Yes, when idling and driving.
Loose motor mounts.
Sounds like a misfire caused by electric supply to plugs.
I sat in my car in the driveway with the car idling, waiting for the kids to come out.
There are a few reasons why a car shakes when idling at a red light. Some reasons could be the ignition coil, motor mounts, or spark plug problems.
a longer cam shaft will make a car idle rough
Your power steering pump and or steering box may be about to give out on you.
yes
bad/partially blocked catalytic converter. - kind of a rotton egg smell, right?
no that would be a mount or a tire or a rim.