FAIRFIELD — It’s cold. You want to warm up your car before heading off to work or school. You go out, start the car, and go back in the house.

The car’s in your own driveway. What could happen, right?

What could, and has happened, is that your car will be stolen, police say. Ask the Hulls Highway resident who left their Jeep Grand Cherokee running around 7 a.m. Saturday. He went back out at 7:35 a.m., and the SUV was gone. It was found a short time later in Bridgeport, where it had collided with yet another stolen car.

“It’s a statewide issue,” Fairfield Lt. Robert Kalamaras said. “The goal is to make our town less appealing to this type of crime.”

And the best way to do that, Kalamaras said, is to get residents to lock their cars, and take any valuables inside with them. “I don’t know what more we can put out there,” he said.

From Nov. 3, 2016 through Jan. 2, 2017, Kalamaras said 15 cars were reported stolen from Fairfield. In all but two cases, the keys, or key fobs for cars with a push start, were left inside the unlocked vehicles. During that same time period, 70 cars were rummaged through and items stolen, and in all but three instances, the vehicles were unlocked.

In all of 2015, there were 26 cars stolen, Kalamaras said, but five of those cars were all taken in one incident from the Mercedes Benz dealership.

“We’ve made several arrests,” Kalamaras, through investigations and some sting operations.

Police believe that Jeep stolen from Hulls Highway was used by a group of teens who had been passengers in yet another stolen car being pursued by Westport police. When their driver took off, they took advantage of the unlocked, running Jeep.

In another case, police tracked down the alleged thief through receipts for baby formula found inside the car when it was located.

Roman Nieves, 37, of Sherwood Avenue, Bridgeport, was arrested Jan. 6 on a warrant for that theft. According to police, Nieves stole a Ford Escape from Sherman Street Oct. 19. It was recovered in Bridgeport Oct. 31, and several items found inside did not belong to the Ford’s owner. One of those items was a receipt from Price Right in Bridgeport for baby formula.

Security footage from the time and date on the receipt was checked and was traced to Nieves’ girlfriend. Nieves was allegedly also seen on a Birch Road homeowner’s security video entering her Land Rover, as well as pawning items from the Ford Escape at Bridgeport’s East Coast Pawn.

During the investigation, Nieves told police he usually just took change from cars and that he only entered unlocked vehicles.

The cars that were stolen in this recent flurry, Kalamaras said, are taken for joy rides or used while committing other crimes, like going into unlocked cars and stealing purses, wallets, phones and laptops left there.

“What we have seen, through surveillance videos, if the car is locked, the suspects will move on,” Kalamaras added. “They are targeting people in residential neighborhoods, and vehicles that are left in driveways.”

He said security video from private homes shows would-be thieves “pulling on door handles, looking for an opportunity.

greilly@ctpost.com; @GreillyPost