[Tannaton]

^^^^ what he said… also has the car been laid up recently? If it’s not been driven for a month or more the discs can corrode but tend not to where the pads are in contact with it, when the car is used again most of the surface rust gets scraped of but some of it gets polished and that leads to a situation where some parts of the disc surface have a surface with different friction properties from the rest, hence the vibration. Try doing 5 or 6 hard stops from 60 mph (with a few mins between the let the brakes cool) see if that improves it.

If it is the above it would likely show up on a mot brake roller test