I'm trying to understand better about your situation. Was the Shell gasoline the same 93 octane or lower?
Hyundai indeed has in some models the requirement of using gasoline detergent, it is written on the owners book. This requirement is because when reaching the fuel injectors the gas tubes are very narrow. The gas tubes are narrow to use the minimum of gas to enter the chamber and explode and cause the motion of the pistons. It is a system to save lots of gasoline using the minimum of it to cause the spark..
If you weren't using gas detergent from time to time, then the jumping of the engine -like if one or more spark plugs stop working- will be felt at any moment. What it happened to you can be caused by dirty or low quality gasoline or, because your car requires gas cleaner every such and such running miles and you never did it.
I asked you if you used a lower octane gasoline, because by doing so the car will act making a weird sound in the engine, no jumping will be felt but will sound as a bad diesel engine. Well, Hyundai cars sound most of them as diesel engine cars anyway, but a bad diesel engine sounds like Rambo's machine gun as background.
Check your owners book to see if your car model requires gas detergent from time to time. If it does, then play safe and use gas detergent every one or two motor oil replacement. It is just about 3 to 4 bucks every 3,000 - 5,000 miles, your pocket won't feel the cost and your car will work like a champ.
