Got to admit that I never had to do that - Pip was an excellent sleeper - and once Alice provided I kept her downstairs until she fell asleep it was fine.
It saves fuel, but surely the starter motor will wear out sooner?? And that wont be a normal starter, it will be a very expensive one. My concern is... what happens IF it doesnt start when it needs to? answer... you are stuck in a junction and therefore at risk of having an accident. Thats not going to save you money either My driving instructor taught me NEVER to turn of the engine while waiting at lights. And yet here we are with cars that turn themselves off!!
------------- Never look down at anybody....
.....unless to offer a hand, to help them up