I've had my 2018 Touring for a month and it's got 1000 miles. Most days I only need the battery and I always leave the car in Econ and do not engage HV mode. On Saturday I took a 150-mile trip and the car behaved as expected. But since that trip, whenever I turn the car on in the morning the engine runs for about five minutes and then shuts off again. This is baffling since the first five minutes of my drive involve coasting down a mountain. Does anyone have an explanation for why this engine runs?