Sounds like it’s in ‘Adaptive’ mode. This also threw me when I had an iX1 on test for the day. I couldn’t understand why it would brake at certain times and not others, until I realised that it was ‘reading’ the road conditions (bends ahead etc). I found it really disconcerting. The iX1 has the newest iDrive OS9 system and I found it to be way too complicated. I had to Google how to adjust this as the menus weren’t intuitive. I don’t know if the i4 is the same, but even on the lowest setting the car still adopted a degree of regenerative braking. You couldn’t disable it completely so that it just coasted when you lifted off the accelerator. I appreciate that this is possibly a characteristic of many EVs but it was a major reason why I decided not to get the car. It didn’t drive as I do and also it didn’t drive like a BMW normally does.