It can be very difficult to find an alignment shop that will get an older Mercedes aligned correctly. I have had MB dealer shops get my car completely wrong.
By the way, to answer your question directly, it is most certainly an alignment issue when the inside edges of your front tires wear excessively. I have been driving a 1982 300 TDT for about 20 years and until I found the alignment guy I have been using for the past 8 years I had a terrible time getting the car aligned correctly. I have had several pairs of front tires ruined by bad alignment causing the inside edges of the front tires to wear prematurely. I always keep an eye on that because it can become a safety issue pretty fast if the alignment is out.
Those "computer alignment" places seem not to have the correct parameters for the older Mercedes in their memory banks.
The guy who aligns my car now does not use those swiveling circular metal plates that the computer balance systems use. He has an old fashioned grease pit. He pulls the car over the pit and has a long steel caliper like a giant micrometer that he uses to accurately measure the distance between the front rims at the front of the front wheels and the rims at rear of the front wheels and then sets the toe- in to the proper specification. I have not had a set of tires ruined since I started taking the car to the guy. He is not at a chain store type of shop, but at a locally owned place called T&T Wheel Alignment and Tires in Ridgecrest, California. I have aligned cars myself using a grease pit and just a tape measure and gotten them close enough, but the steel caliper method is much more dependably accurate. I would prefer a backyard alignment with a tape measure to one of those computer alignment places. When I was farming we always used that method to align the tractor.
You might think the camber being out is what is causing the inside of the tires to wear, but it is most likely the toe-in. Camber is the lean of the tire relative to vertical, so if the camber was out and the wheels were leaning top inward the car would be riding on the inside edges of the tires, causing them to wear abnormally. Camber has not usually been a problem with my 300 TDT.
If your car pulls hard to one side the caster may be out. Caster is the measure of whether or not one wheel is in front of the other. It's the measure of how far forward or backward the wheels are relative to the front of the vehicle and they should be at the same point relative to that.
But, again, toe-in, if one wheel is more to one side than the other, can also cause the pull and countering that pull is what wears out the inside edges of your tires.