If your car is trying to regen every couple of days, then it thinks the previous one didn't finish the job, and still got more to do.
If it needs a catch-up then a 20 minute trip is far too short, probably looking at a 30 minute regen starting from when everything is hot enough. Which on a cold winters day is likely to be 15-25 minutes. So going to need at least 50 minutes use. Once back to regular regens back to nearer 25 minutes (plus about 10 minutes extra in cold weather).
Without knowing the service or usage history, there is a chance previous owner did lots of short journeys too, if too many regens are incomplete tend to get an ash and soot build up which sort of bakes on and a regen won't ever fully clean. As previous replies have said, can scan for the ash level which will give you indication of how clogged the DPF is.
Don't want to be bearer of bad news, but if too badly clogged will need a DPF clean, not cheap, and if only had it a few weeks best bet is to get supplying dealer to fix it as a fault developing at time of sale.
Your problem is if you mainly do town driving and only occasional other journeys then the emissions system on a euro6d diesel will keep giving problems. A diesel doing a regen uses more fuel than a petrol. So really you have bought the wrong car, and should have got the petrol version. The diesel is not efficient on cold short journeys, diesels are best when warmed through, remember the WLTP fuel figures are tested at about +23c (and not during a regen).
I wouldn't compare it to an older diesel without latest emissions equipment, they didn't have to spend some of their life (and lots of extra fuel) cleaning and burning particles at high temperatures. Diesels are now a liability if they are unable to fully regen because sensors limit things until they do to meet emissions requirements.