Buick LeSabre Shaking at Low Speeds

I have a 1995 Buick LeSabre with just over 100,000 miles on it. Recently it has begun to shake at low speeds. The car shakes as if it were driving over a rough gravel road, and makes a sort of chugging noise when I step on the accelerator at speeds from 15-25 miles per hour. When I accelerate beyond 25, the shaking stops, and the car stops making the chugging noise as well. It drives beautifully on the interstate, but horribly when I am in town. After taking the car for a drive on the interstate for about 30 minutes one day, the shaking at low speeds actually ceased for over a week, but then came back. The “check engine” light has not come on. I maintain the car regularly, getting oil and filters changed, fluids filled, etc. I’m wondering if this sounds like it could be caused by a problem I can fix myself, or if I need to have the car looked at by a professional. I would appreciate any advice! Thank you!

OK, nobody replied, so I’ll take a stab at it.

Vacuum leak. Might be tough top diagnose, but once located, easy to fix!

Thanks for the comment! I’d given up on the posting here, but I’m glad I checked back. I’ll check for a leak! Thanks again!