If you buy a vehicle from a garage then you may have some sort of warranty. This is not guaranteed and you need to check before you agree to the purchase what you are likely to be offered. Many warranties only cover major components though so you could find that only a handful of parts are covered. The warranty can range from around one month upwards of 3 years and sometimes you can pay to extend the warranty. The warranties are often sold and managed by a third party so it is important to get the details of who to contact if there is an issue.
If you notice that your garage has developed a fault quite soon after you have picked it up and it is still within the warranty period then you may wish to contact the garage directly as they may well ask you to pop it back in. If it has been a while since you picked the car up then you may decide to just go straight to the warranty company. They then may ask you to take the vehicle back to the garage or a repairer of their choice or if it is not safe to drive, they may get it recovered for you.