Problems with shifting

I have purchased a 2005 Buick Lacrosse CXL with 80,000 miles on it. I have had it for almost two months. Since purchased I have had it back to the dealer at least ten times for them to fix problems or look at the car. They replaced a hub bearing and the motor mounts. I also had a diagnositics test performed on the car and nothing was found. However this car sometimes acts like it does not want to shift into first gear. When driving it takes a while to shift and the first shift is not smooth. It doesn't do it all the time and after the motor mounts were replaced it didn't do it for a few weeks. But the past two days it seems as though it hesitates to take the first shift but after that it rides smooth.