Transmission problem
2000 Hyundai Sonata 4 cyl Front Wheel Drive Automatic

my car is recently experincing problems with the transmission, it starts out normal, but then jolts (bringing the service engine light on) then hesitating to shift gears, then running the car at 55mph in the same gear not allowiing to kick in gear. Also hesitant to taking off. I have to stop the car and turn off ignition, and restart engine to reset. After that happens, it;s fine for a mile and starts all over again. Also it shakes alot even at 55mph. please help me understand what the problem is. Thank You, Pete