vibration

had my audi for 5 -6 months

iv noticed well my friend brought it to my attention when he was sitting in the passenger seat in the front, mainly long drives like motorway i notice it kicks in more, well its sounds and feels like a phone is vibrating, it sounds repatative and can only hear it if car volume is off, if you sit in the front passenger u can feel it for sure,
its sounds like a 3310 vibrating for like 2 secs then goes of for 1 then on for 2 then of for 1

my car doesnt all ways do it, its random, so it comes and goes i thought it might have been something to do with my ac so i turn it off but its still there
its so frustrating my friend noticed it and so did my brother when we went down london

i think its like a mechanical pump vibration pump sound? i have no lights on my dash and my car was bought from a dealer and its straight not previously crash damaged etc

any experts out there?

lane assist? i dont think its in my spec? how would u know?

cant be a dodgy wheel weight as it dont always do it, and when it does its so precise asif a phone is in the glove box vibrating not in a constant way but a very rythmic way i will jump on the motorway tomorrow lads and try trouble shoot and pin point more into depth