Wait a minute, you just might want a direct answer to your question!
2014 Mercedes Benz E350 sedan. It is recommended by Consumer Reports above all other midsize luxury sedans, and in all recent years, not just 2014. CR says they are highly reliable. The 2014 did have electronics problems, and that should have been taken care of as part of the warranty if encountered. I recommend 2014 since the largest part of the depreciation will be gone already. Higher mileage examples might be on the dealers lot for a bit over $30,000. Low mileage versions will be closer to $35,000. These will almost all be off lease cars. Pay attention to the CarFax review of these cars. Since they were likely maintained by a dealer, there should be a lot of data available. I've been looking at them in my neighborhood, and found one at the closest dealer that I would consider, and about 8 that I would not, all based on CarFax data about where they came from and the maintenance/accident history.
My second choice would be the Audi A6. It is slightly less reliable than the E350, but has a well regarded turbocharged 4-cylinder engine. Both use premium fuel, if that makes a difference, and I would recommend using only premium in these cars. While there will be few repairs, maintenance will be expensive, as I'm sure you know.
Let us know what you decide!