Car shakes

I had my brakes done last year and after 4 months of driving the car started to shake on the passenger side, I brought it back to the garage and he replaced the disc again after 6 months later the car starts to shake again. They didn, t put original parts on andI noticed that in the winter the car don, t shake at all but as soon as it gets warm outside the car shakes. We got the calipers checked and he said it was ok so its not the caliper and now its over 1 year and the warranty is over. So what can the problem be if it shakes when its warm and not when its cold?When I go over 50mph and try to stop the car shakes so bad that I need at least 3 car lenghts to stop. Can it be the disc are not thick enough or what?Any help would be greatly aprreciated.