POSSIBLE TRANSMISSION PROBLEM? on 2001 Hyundai XG300

My check engine light came on several months ago; now the car seems to not accelerate especially past 45mph. I appears to jerk as if it's changing gears.
I've kept it maintained, oil changes, tire rotations, brake jobs, etc. What could possibly be wrong?
thanks for your help

1 answer 1 comment
You need a mechanic with a scanner to read trouble codes from the computer. if the check engine light's on then there are codes stored in the computer that would be a big help in diagnosing the trouble. Check your transmission fluid, hot. Should be up to the mark, not overfilled and the fluid should be pink and clean.
Thank you Superbob, I will take it to a mechanic, or would you recommend a transmission specialist like Aamco?