Outdoor cats will sometimes seek shelter under the warm hood of a car, only to suffer injuries by the fan when the car is started up in the morning. A few years ago, my husband and I found a very small kitten trying to cross a busy highway at an intersection. We were able to catch her and bring her home to keep her safe until the owners could be located. Later we found that she had climbed up into the undercarriage of the owner's SUV during the night, and somehow survived the ride for several miles until he apparently stopped at the traffic light and she jumped or fell out. This is not an unusual event, and most cats do not fare as well as this kitten did. Make a habit of honking the horn before starting the engine. Any cats that might be lurking there will flee, for sure. OR, if you leave for work in the wee hours of the morning, do as reader Barry J. does, and pound on the hood. It will accomplish the same result, and keep your sleeping neighbors at bay.
By the same token, it's a good habit to just make the garage off-limits to cats. There are too many potential hazards there, including antifreeze, which is tasty but extremely toxic to cats.