It's normal, and even has a name: "Sprout and Pout".

^ Right. Although you assume the grass is doing nothing, it is actually working on root establishment rather than top growth. Don't worry about it, just mother nature doing her thing, although it's not very satisfying to watch.

How well watered are you keeping it? By now you should be backing off on daily watering and extending the times you are watering. Eventually you would be watering once a month and that eventually will be coming real soon as the temps cool off. Then next spring adjust the frequency to keep the grass alive.

Measure how much water your system puts out by placing cat food or tuna cans around the yard. Run the sprinkler and time how long it takes to fill the cans. You should be applying for that length of time, once a month in the winter and once a week in the summer. If you do more, you risk losing the grass to fungal diseases.