Im not a car geek, and therefore, do not know tremendously much about them on a technical level (or any). I always loved the old 70s Mercedes S Class (w116) range of cars, but they are 10-15 grand in decent condition. Too much for a first car.
Couple hard truths...
There is a really high chance you will wreck this car, being your first. If you don;t odds are it will get wrecked anyway. Buy something MUCH newer, it may save your life. Don't get something too new. You don't need the distractions. Get a manual if yo can, it will keep you engaged in actually driving.
As for your choice in cars themselves...
If you think $15k is expensive, wait until you see the repair bills. A high end car from the past, particularly a luxury car, still requires upkeep and parts that cost what they would for a car of that caliber today. If an alternator on a new $100k Mercedes costs $3000 today, the alternator for a 1970's Mercedes is probably going to cost $3000. Age doesn't reduce wear and tear or the price of parts.
This goes double for mid 80's and earlier eurpopean cars.
These cars were usually not imported here by the manufacturer, while legal they are known as grey market cars. Limited numbers means limited parts. As soon as they were legally imported they had a MASSIVE luxury tax added to them. So while you may think an entry level Mercedes or BMW is cheap, it wasn't. Go look at late 80's BMW low end 3 series interiors, they were sparse. Yo coudl get similar on almost any other low end car, the difference was yo pad a huge tax to have that badge on the front.
And then we have Eurpopean reliability.
Look I loved my BMWs, and I have been in some really nice Euro cars in general, but their reliability is terrible, especially as they age. You don't need to spend half your time wrenching to keep your first car running.
You are not really going to get anything for $5k from Europe that will be remotely reliable and in good shape. It won't happen.
My advice is the same as TP and sncbraxsc2, go Japanese, you will get FAR more for your money. Specifically, look into a Lexus or Acura, you will get similar to a European car without the cost or hassle. Used parts are a breeze to find, and way cheaper and if you do need to go new, it will not cost as much as you paid for the car to fix it should something major happen.
There is also a method to this madness... Go with the right car now and it will give you experience, and save you money, so you can later afford the one you really want, as a second car. Having two cars was the only way I could really enjoy some of my favorite cars. Buying the wrong car will keep you tied down, eating all your money and keeping you less mobile.
Skip anything German, hell, skip anything European. Double skip anything high end. Run far far away from anything that matches those AND is a luxury brand. For American cars, those are kind of all over the place, and you probably wouldn't like your options (as strange as it sounds... Buick). Korean, believe it or not, is not a terrible choice, for what you could get for $5k, you could do quite well, but I have a suspicion you would turn your nose at that idea (I kind of would too). Which leaves Japanese, right back where we started.