general problems of the 2006 Nissan Sentra

My 06 Nissan Sentra, that I purchased to replace the taurus that the frame failed has a prob. With the cruise control-- when in cruise, going down the road, when it needs to keep up to speed, it shifts down two gears, instead of one, and the speed increases faster than it should, and then it shifts up one gear, then back to drive-- there times when if the driver is not used to it-it gains on the traffic in front, faster than any other car I have driven, and if the driver is not very attentive it could cause an accident or at least scare the driver, and cause them to over react, in my opinion. This is not right and should be looked into before someone gets hurt. . We do not therefore use the cruise-- this has been happening ever since the car was new-- and when I called Nissan and the dealer, they said it prob. Was normal, not a good enough answer, in my opinion-- it is almost as bad as the Toyota prob. And I think it is all in the electrical set up, which I think is going to be the downfall of the modern cars. It was not necessary to complicate something that was working right for years, and not they want to make the brakes electric. To much electric junk to go bad and cause problems, and all so the veh,'s have to be taken into the dealer or shop. To have expensive repairs, and cause prob's with inspections all the time, also expensive, and not warrented thanks.