What should I look for in a used Mercedes E-Class saloon?
Unlikely as it sounds, this vintage of E-Class can suffer from rust around the front wheelarches. It doesn't affect every car, but it's a common enough problem for it to be worth your while having a good look and peering underneath the plastic wheelarch trim.
The engines are rugged units and will cover incredible mileages if they're serviced on the button, so the most important thing to look for is a full service history at either a Merc dealer or recognised specialist.
And, while you're about it, look at the service file to see if the front suspension bushes have been changed, as they need replacing every 60,000 miles. Also look at the front tyres to make sure they are wearing evenly.
Finally, there have also been a few minor electrical niggles reported, but nothing that is not easily fixed.