It's a possibility that you don't realize you are activating the cruise control with your hands on the wheel if you have cruise control otherwise you may have an exposed wire for it or for the throttle position sensor and when it makes contact the speed increases you must check all wires going to the throttle position sensor and to the cruise control the buttons on the steering wheel maybe sticking and activate the cruise with out you knowing it try heavy cleaning here and see what happens also if all is good in the wheel and throttle position sensor wiring drop the inner fenders and inspect the wire harness that runs down each side open it up and visually inspect those wires for open insulation that would allow contact to be made and if you do find that it has to be more than 1 wire that's exposed to give power to the other one ok or it could be grounding out against the fender sometimes mechanics will open wires checking for shorts a bad practice and then leave it like that and when there's moisture around the wires are arching to ground which can burn a whole in another one or two wires insulation also rusting fenders can cause the wires insulation to cut open from vibrations from driving so that's what I think can be happening here also faulty cruise switches good luck stephen

I take help from online websites that have this service like helping in repair some like reliable-store have instant help.. others are a bit slow which I don't prefer... rest is up to u.. U can also get free manuals