Bucking at constant speed? Options

[6GenCircleLghts]

After I've been driving for 10 minutes or so and I'm going down the road in 4th at 35mph with my foot barely on the gas pedal. I don't get massive bucking but enough that it annoys the hell out of me. It also happens when I'm in 3rd going 25mph and 5th going 45 to 50mph. Two main things that were replaced were the timing belt and distributor. Though I got the distributor replaced a couple months after the timing belt and that is when it started happening. Would it be from the distributor or what? The timing belt and distributor was done by a professional mechanic. I did the starter by myself, plugs and wires, but these were even before the timing belt/distributor.

[DGAF]

I could be a misfire. But then again the way you describe how you do 35 in 4th gear by barely touching the gas pedal I think that it's just like 95CelicaST mentioned. You may just need to downshift and problem solved.
but you mentioned it happened after the timing belt replacement. Maybe the mechanic who changed the belt adjusted the timing on the distributor and that could have caused it for you to notice the difference right after the timing service. I would just double check it with a timing light just to make sure it's on point. but then again it could also be your driving... Good luck and hope you find a solution to this issue