Take it to the dealer right away since the car is still under warranty. There could be a radiator hose leak or other. You certainly don't want to get stuck somewhere if something else goes wrong. Be proactive. I once bought a new Mazda years ago, go on the freeway, had a flat and found they had put a tube in the tubeless tire! Clearly told me they were underhanded. It was the worst car and it was in their shop more than I drove it. I was glad to unload the lemon. I even wrote to Mazda headquarters and got zero customer service. I would never buy one again.