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You may want to check that the shop (not a Hyundai dealership?) replaced your filter with the correct filter, and the correct weight of oil. Many newer cars are extremely sensitive now, and having the correct viscosity of oil at startup so that valves open correctly, etc can be very tricky. I know the new Dodge Dart is very finicky, if you let it sit for a month it won't even start unless you crank it for a few minutes to pump up the oil pressure.
Also, did they read the fault codes that were stored? That should give a vital clue as to what system is being affected.