Hi, new here so apologies for any errors

i have an odd issue with my a4 b8 avant auto diesel.

last week I started feeling some low level vibration while driving. It’s intermittent & inconsistent. Sometimes it’ll kick in above 70, sometimes down to 40, sometimes not at all. Sometimes 5 mins into a journey, sometimes an hour, sometimes never. When it does happen, if I’m not braking it feels like a vibration due to a dodgy road surface. If I brake when it feels like that I get strong judder. If it’s a time where I’m not feeling any feedback while driving there’s no feedback through the brakes either. In any case there’s no pull to one side when I brake.

I took it to a garage last week who showed me the driver front was binding slightly, so we thought that was the issue & replaced the calliper. It drove fine for a few days and the. Today an hour into a 90 min drive I had about 15-20 mins of the vibration symptoms as above again. I’ve driven it since with no symptoms.

I’m going to try getting the wheel balance checked tomorrow..but I’m not convinced it’ll be that. Has anyone else experienced this, solved it, or know what’s going on please?