I own 2001 Kia Optima LX, it has 121k mil...

I own 2001 Kia Optima LX, it has 121k miles on it.
I own 2001 Kia Optima LX, it has 121k miles on it. The check engine light is on, and recently it jerks when moving. It does not pickup speed. It moves at 20-40 miles/hour, then after a while it picks up speed. sometimes it just turns off and locks the steering wheel on the spot. The car is a More
I own 2001 Kia Optima LX, it has 121k miles on it. The check engine light is on, and recently it jerks when moving. It does not pickup speed. It moves at 20-40 miles/hour, then after a while it picks up speed. sometimes it just turns off and locks the steering wheel on the spot. The car is a manual transmission. Any idea of what could be the problem. I have also noticed that it does not idle. When it is cold it appears to run ok, but after 10 minutes it appears to be starving for gas. i do not know how old the timing belt is.