Back in 2018 I was toying with getting a new C Class, after having had one of the previous generation. I am 6' 4" and about 14 stones. I found the seats all very narrow and hard - my back was resting against the bolsters each side.. Went to Lexus instead.

Firstly, why on earth would you buy a car you can't get comfy in?.

Secondly, given how you feel about the seats, get rid of the car and replace it with something you can get comfy in.

Good question - 20 minute test drive it felt fine. 45 minute drive home it started feeling uncomfortable. I’ve never had a car that had uncomfy seats before. Previous car was a 2018 Picanto and they were perfect! It didn’t even cross my mind that a modern car could have poor seats...

Had a few Mercs with no problems getting comfy, I just experiment with the plethora seat adjustments 'til I'm ok.

The problem is not with the seat position, its with the width of the seat between the bolsters - I know exactly the problem the OP has. I am pretty broad (not fat) and the seat is too narrow. It surprises me a bit because I thought, on average, Germans are pretty broad too. Older generations of Mercedes were much better, it seems a modern trend. I recently drove a Fiesta ST and it was terribly uncomfortable because the seats were so narrow.

Lots of car upholstery specialists/ trimmers are listed online. Many of them mention improving comfort. Also maybe an independent Merc specialist can also alter the bolster or recommend someone who can? Main dealers will not be interested.

Of course an alteration may still leave the seat uncomfortable so it’s best to find someone who has actually solved the issue before.

Meanwhile I wonder if you can set the seat very low and get a piece of dense upholstery foam cut to fill the seat between the bolsters to reduce their effective height. It’s not a permanent solution but it would confirm if it’s just a bolster issue?

1) I am a 6 foot tall broad (not fat!) 14 stone man.

According to the NHS BMI calculator you are, ahem, overweight.

All ideas welcome.

1200 -1500 calories a day for a few weeks

Thank you for your helpful input. So does this mean Mercedes should test a persons bmi before they buy?

I will immediately stop working out at the gym, stop playing rugby, and go on a crash diet....but it still won’t make my hips narrower.....maybe surgery is required. Yes, surgery so I can have my bones plained so I can fit in a Mercedes seat....

Or Mercedes make wider seats in their cars?

I am somewhat perplexed that Mercedes is for very narrow build people only.

My view is that if you can't get comfortable on a car then best to change the car. This is why an extended test drive is very important. Usually uncomfortable feeling starts to appear after 45-60 minutes of continuous driving.

Mercedes steering/pedal offset is often mentioned as problem for RHD markets. This is another reason why I prefer Japanese cars. Surprisingly Korean cars also work better for me even though they are LHD in base country. Never owned Volvo, but heard their seats are very good.