Most likely culprit, dead battery. After an average of four years in the Florida heat and especially when in a hot garage, the life expectancy of a battery is a lot less then if you reside in a more temperate climate

My experience, batteries have a shorter lifespan in extreme heat conditions. I think TV fits that situation.

Newer cars, and 2015 qualify, have a large number of electronics, many of which you are only aware of occasionally but are still live. If you start the car and let it run only a few minutes in the garage that is not enough to recharge the huge drain that is taken from the battery when the car was started. When I was working, I used to have a 2-mile commute, and I went through batteries faster than expected because even a two-mile drive is not enough. Any car that is occasionally used should still be driven ten miles a week not just for the battery but for the suspension and engine lubrication. Running an engine for only a couple of minutes is just enough time to build up water condensation and not dry it out. The engine should be run long enough to fully open the thermostat. If you are just worried about the battery, get a battery tender. They are easy to use and can be quickly connected and disconnected.

Thanks for the thorough, thoughtful & informative reply! A battery tender may be a good investment for me. I do try to do as you say but driving it even when I don’t need to is not always easy to remember to do. I love having a car but I really don’t NEED one most of the time.

Battery
 

Expensive batteries don’t mean they are better

You should always use a factory Mercedes battery. Call Mercedes Roadside..You will be charged a fee if you are not a member but they will come to your house to replace the battery with an approved battery. Mercedes are finicky.

I'd start with the simplest. Disconnect the battery, charge it and see if it holds the charge. if not move on to the recommendations. Florida garages can get very hot. Get a quote from AAA, assuming you belong. Up north they were about the same as the auto parts stores and they come to the house, test it and install it. If you drive to the auto parts store, call first and make sure they have it in stock.

OP, did you find a solution to your problem from all of the suggestions, if so, what was it?

Lived in Florida entire life. Batteries last 3-4 years. Heat and batteries= not good