This. I see a lot of people, especially women, pedalling on tip-toes with their feet pointed straight down at the bottom of the pedal stroke. This causes your pelvis to rock around the saddle with every push of the pedals.
Some Specialized dealers have a wall of red and white test saddles that you can sign out and take home to try for a while. This time of year, if you're riding indoors on the trainer, is a perfect time to test drive saddles.

