While those on the outside may see what you do as sitting down for most of the day, any delivery driver will tell you that this is far from the restful role that some may think.
Getting in and out of a car or truck multiple times a day can lead to stresses and strains on your body, not to mention the potential for injury from lifting and carrying.
There are certainly many sources of advice about driving safely, using hands-free devices, lifting with your legs etc., but here are a few you might not have thought of:

1. Keep your car vehicle cool in winter, not hot, and cool, not cold, in summer; sweating with your vehicle at 25 deg C with your winter coat on, while its minus 25 C outside can really stress your system. Constantly exposing yourself to large temperature changes getting in and out of your vehicle dozens of times a day can promote ill health. A sick driver is nobody’s friend.
2. If you smoke, quit. That’s right, quit. The opportunity to smoke far too much, and leave many cigarettes just burning away in the ashtray is just too great. It’s bad for your health, leaves you open to getting sick (seem point one), and is super expensive. Plus customers don’t like the smell I can guarantee it.
3. When you are exiting the vehicle, try to avoid stepping down and twisting your leg as you climb out. This puts a great deal of repetitive strain on your knee, which can lead to discomfort in the least, and maybe major problems.
4. Know where you are going before you leave your last delivery. With GPS this is much easier today, but ensure that are stationary when you confirm your next stop, not already rolling out of the last customers driveway into traffic, trying to plug the next address in or, for the old schoolers, checking your delivery sheet.
5. Ensure that any heavy parts are secured outside the passenger compartment. While we don’t like to think about collision, they do happen and doing something as innocuous as putting an alternator on the front passenger seat can make a relatively minor collision very serious when that part becomes a projectile.