A sensible question to ask. It all comes down to the health of the entire electeical system. Grab driver, your car must be newish right? System should be fine to turn on and off.
The situations where it would be a problem...
An aged battery, would take a significant boost charge to recover after every start compared to a newer battery. So if you constantly did this stopping and starting on an older tired batery, 2 bad things would start occurring.
1. The current going through the starter motor would start increasing and starter motor life would be shortened due to the resulting heat, and
2. The current needed by the alternator to replenish the significant discharge that the older battery took when supplying said current to the starter, would start increasing, shortening the life of the alternator.

So put simply, stopping the engine is really economical, only if your batterys health is at least 70%. If the health is lower than that (as measured on a decent industrial workshop battery tester) then you may actually be expediting the death of multiple electrical components beyond the value of the fuel saved.

One more factor, is fuel type. Diesel engines are significantly more efficient at idle than gasoline. So the battery health threshold for where this economical cutoff would be for a gasoline vehicle is slightly lower than an a diesel. i.e, a gasoline engine might be better off switched off rather than idling at 70% battery health, but a diesel uses ao little fuel at idle it might better left on, unless battery health was so good it did no harm to the battery health.
I hope that makes sense.