Car SHakes when gas pedal is pushed, or won't go up hill, check engine blinks

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Problem happens all the time. Whenever I try to push the gas pedal, my car violently shakes, and won't accelerate, check engine flashes, a minute later the car is running again smoothly, until I have to go up a hill, or statt accelerating faster. And not a little shaking- but violently. My car won't go. Terrifying to have to drive half of the time. Help someone, I know nothihng about cars, and am on a limited budget.