Jerking & stalling.

What is your question?

I live in a small town where the car performs fine, even up & down steep hills, but after I've been driving on the interstate for 25 or 30 minutes it begins to shake & jerk. The RPM's will go up suddenly, as if I've mashed the gas pedal to the floor and then it will jerk and act as if it's going to stall. If I turn the engine off for a few minutes it will do OK for a bit and then start all over again. I know it may be hard to diagnose the problem but any help you can offer would be appreciated. I'm a single, middle-aged female who lives alone so I need to keep this car going as long as possible, at least until I can get it paid for!