Hi Papu21, I do not know where is the best place to buy a car. If you buy from the dealers, it is of course safer as you have warranty and after sales service. Servicing a car and getting spare parts in Doha are some of the biggest concerns when buying a car. We have been advised to buy Toyota ourselves. One website is: http://www.toyotaqatar.com/Contact.shtm
We are getting a new car. If you are getting a used car, you will need to check it or get it checked out for you, especially if you get one of the big cars as some of them are known to be used over very rugged terrain and could be quite worn down. Plenty of used cars for sale advertised here in QL. The risks of buying used cars from private owners are the same as elsewhere.