
It is comfortable and lazy.
With mine I tend to find it starts when your speed is too slow for a trot for the puppy so they slow down and pave. Your walking speed is probably too fast for a dogs walking speed, but to slow to get into a trot. This then becomes a lazy habit, and they can then do this faster nad faster.
You need to break their stride. I usually give a tug up and forwards as we head off, also if they pace, then I go back to the start and say trot. They soon learn that if they drop back into pacing they will not get very far. Moving at a fast enough speed once the stride is broken out of the pace is important.