Classical and vintage cars are very gentlemanly, especially with collectable value, if convertibles or have other iconic pedigree.
On new cars, there are two main schools of thought. The old school goes for established British marques, so long as they are not Rolls Royce, because that’s the preference for Middle Eastern arrivistes.
So a Bentley or an Aston Martin will do, as will a Landy or a Range Rover. Jaguar is tricky, because UK arrivistes had taken to it.
As a general rule, avoid anything Asian or continental if it’s new, unless it is a highly-successful reboot of an iconic car. So BMW is out, I’m afraid, because that just screams ‘I didn’t always have money’, as is Mercedes, which screams 'Successful dentist’. If you want German, rather go for Audi, because their timeless design has an air of understatement.
(Yes, and avoid Porsche. That’s too vulgar nouveau riche to even consider.) Up north, some Volvos and Saabs have cred, but their design is so often so crushingly middle class that I do not consider them by default as suitable for under 70s.
When it comes to American cars, anything mass market won’t do, but Jeep is generally safe. Buick and Cadillac have been demoted for being too gangsta for too long. Avoid like the plague anything that resembles a pick-up truck, however muscled - Ford’s successful marketing has given them a macho gloss in their target audience’s minds back in the 1990s, but they are yet to shake off their proletarian origins.
Young fogies have a different approach, one that avoids conspicuous consumption. You get a Wrangler because you regularly go to stables or to the countryside and need it, not so that you show off. You drive a (thoroughly reconditioned and reconstructed) vintage car, because of its classic design.
Small Audis and Mini Coopers are great, because they have all the fun about driving them, but do not seek to gather attention. Econo-gents drive more VW Polos that one would imagine, to the approval of other gents.