A Dodge Caravan that shakes?


I have a 96 Dodge Grand Caravan with 260,000 miles on it. Within the last week or so, I’ve noticed that when I’m accelerated and hit some where around 40 mph, the car will start to shake. The shaking stops when I take my foot off the accelerator, and it stops when I get past 48 mph or so and begins to run smoothly again. It seems a little worse when driving uphill. The check engine light is always on (the instrument panel comes on and off and sets off the light) – so that’s not really helpful. Needless to say, I’m getting a new car asap, but I’d like to know what this shaking might be. Any thoughts? Thanks so much for your help!