Volvo: 1997 850 Shakes on acceralte, high speeds, rear end

Question
I have a 97 850 that will shake (it feels more in the rear end, but I could be wrong) when I accelerate mainly to high speeds. I just got it and took it to PA (A 7 1/2 drive) it was fine there and fine until I gassed up at a station in PA. It was shaking worse then it is now, it would do it before anytime that I pushed the gas pedal. The car is fine as soon as I release the pedal or if I am idle or traveling at low speeds! What do you think could be my issue! Thank you so much!

Answer
Jackie,
You will need to take the car in so a tech who can look at and drive the car. Is that shaking only the engine or is it in the entire vehicle? Is the check engine light on? Could there be a miss firing in the engine, like bad gas. I have seen cars with bad motor mounts, bad tires, worn front end parts, missfire due to bad ignition cables, cap or rotor, plugs.