German cars are not at all unreliable when taken care of properly. The w204 which many members consider buying is one of the most reliable models Mercedes has ever produced; it is at least twice as more reliable as a w203 model Mercedes. I own one (w204) and the only thing apart from ROUNTINE MAINTENANCE which failed was the SRS airbag module (which was a costly replacement unfortunately) other than that SINGLE part, the car has been bullet proof. The m271 engine which came in the c180 and c200 kompressor models respectively is known as the most reliable motor Mercedes has produced. Early models suffered from timing chain failures but engines made after the mid of 2007 had stronger teeth on the timing chain which didn't wear out as quickly. The 5G tronic gearbox is known for its reliability and robust nature.
One thing to note when buying any German car is to THOROUGHLY CHECK the service and maintenance history. If everything has been done by the book, its highly unlikely that something will go wrong unless the owner does something stupid. Most people on PW prefer saving a mere few thousands by not getting the car inspected prior to their purchase and then unfortunately they have to suffer from the issues the car has to offer. One thing more that people don't realize is that the cheapest Mercedes is often the most costly in maintenance. There is always a reason why a car is selling so cheap, no owner loves depreciation.
Most people in Pakistan put the cheapest engine oil they can find and pour into the engine which ultimately causes problems. When a car is almost 80k kms driven, especially if its something German, you should expect to invest at least 100k rs in it as fluids like the transmission fluid, engine oil, differential fluid will in fact need to be changed because once these cars reach Pakistan, they hardly ever get driven so the fluid itself expires. When routine maintenance is neglected, ANY CAR will be unreliable. Its not brand specific.
Badly abused cars go through a Rs. 30k detailing job and look great cosmetically but mechanically are just lumps of rotting metal and plastic. These cars are what most people buy because they look good (and that's just it).
If you're in the market for a German car, inspect it thoroughly yourself and get it checked by a REPUTED workshop (which might cost a few thousands but will pay off in the future) and thoroughly check the service and maintenance history.
AVOID ANY CAR when the owner says that the car ONLY needed oil changes! There are several different fluids in modern cars which all need replacing sometime, no fluid is filled for life. All filters need regular replacement too.