My 2010 Sonata has trouble changing gear between 35-50 mph at times, begins to shake and seeming to stall but never turning off, resulting in the check engine light turning on. After a while the light will turn off and the car will drive just fine. It also hesitates to change gear while going uphill and the light kicks on again until it eventually goes off again and drives normally. I have checked the fluid and it looks fine and at the right level. The question here is am I better off taking it to a strictly transmission repair shop (AAMCO), a repair shop that does all auto care including transmission work, or biting the bullet and taking it to a Hyundai dealership and paying out the wazoo. Any opinions will be greatly appreciated!