Hello all,
I have a 2015 S60 with approx. 84k miles on it, recently purchased used from a dealership in town. Have noticed a noise (along with subtle vibration under the floor) similar to running over rumble strips on the highway - not quite as loud but similar type of noise. The noise never starts immediately, usually takes 5-7 minutes of driving to notice the first noise but on some drives it won't happen at all. When it does happen, it will happen repeatedly throughout the drive but not in any type of rhythm or consistent pattern. The dealership originally diagnosed bad shocks which they replaced and reset the transmission but the noise continues. Also it is bitterly cold today (5 degrees F) and noticed it seemed to be happening more frequently than the warmer day before - but this could simply be a coincidence. Any ideas are appreciated!

 

is your car FWD or AWD? If AWD, I'd be looking at the center bearing if FWD possibly axles. Other possible sources include transmission/motor mounts and exhaust system components - in particular things that may expand as the car warms up. Normally things like sway bar or chassis bushings are noisier when they are cold and quiet down when the warm up...