Is this normal for a 2019 Jeep Grand Cherokee?

It is called "auto stop". My 2019 Silverado has it and I think that is the stupidest effing thing to put in a vehicle. I am diligent about turning it off everytime I start the truck, however

Stop /start system, most newer cars have it. Supposedly saves some gas but I reckon it wears the battery and starter more , so costs you in the long run. Also, I've experienced it cutting in sometimes when i didn't expect it, so i normally turn it off as soon as I start the car.

Mar 19, 2019 - The vehicle's engine will shut itself off when the driver has the brake fully pressed down and the vehicle is idling, like when stuck in standstill traffic or stopped at a stop light. Once the driver lets off the brake the engine will automatically restart itself and you will be back to driving like normal.

It is normal on lots of vehicles. I believe you can turn off the feature. It does marginally improve gas mileage and that is why they do it, to appease the feds.

ECO Boost is a Ford thing

The stop start system is intended to save gas, but it may not kick in under certain circumstances, such as when the engine is cold, the a/c is running, or the steering wheel is turned. And by the way, eco boost is a turbo and only Ford uses that term.

Sounds like you bought a hybrid Jeep.

Yes, some new vehicles have this to avoid idling and burning gas when you are stopped.  It will be explained in the owner's manual.

Yes, it is the eco-mode, it is saving gas at stoplights

Many new 2019 cars have this built in energy, fuel saver. There is usually an over-ride that can be set so this doesn't happened but it is good for the environment to keep it on. My Range Rover does this, too.

It is the Auto-stop feature - read about it in the owners (aka Idiot) manual found in the glove box.