Car shaking/something burning

I own a 2003 Suzuki Grand Vitarra, 5 speed. Lately it has been shaking when I am speeding on the highway. Not only does it shake, it accelerates by itself. Let say I am on fourth gear, going 40 miles per hour it goes up to 60 without my pressing on gas. The "check your engine light " has been on. It came on right after new brake pads and shock absorbers were put on. I also smell something burning. What might cause this (the shaking and what's burning?)