I've noticed recently in my 2012 Tundra DC that when I come to a stop and start up again or even sometimes when I turn I'll hear and feel a thunk under the seat, almost as if it isn't seated correctly on the rails.
Have you guys heard this? Is it just a product of some fairly cheap seats? Other than this I love the truck.
I had exactly this problem. I ended up getting the seat frame replaced.
In my case, it was a worn or broken worm gear for the seat adjustment (the gear comes as a frame assembly, so they swapped the whole seat frame out).
I had difficulty replicating the problem at the dealership. I took it 3 times, and of course it never did it for them. I'd brake, and the seat would clunk and move as though a bolt was loose. Not every time, but a lot of the time. Rocking the seat made no noise. It was as though the seat was loose, but not all the time. I finally discovered lowering and raising the seat would exhibit the clunk on the upward motion (whilst sat in the seat, it didn't do if if the seat had no weight on it).
Try adjusting the seat up/down or backwards/forwards and see if the seat jolts at a certain position. This indicates the worm gear is faulty. You'll have a lot better experience at the dealership if you can show them the fault on demand.
