Is the sound almost a rumbling sound?
If so then get up to the speed when the sound starts, along a straight quiet road, and turn sharply left and right. If you turn right and the sound becomes quieter or stops but gets louder when you turn left then it is most likely the driver's side wheel bearing.
It starts and stop which ive recently descovered. i somtimes does it, but when it does it makes the sound from when i very pull off back to when i stop again. i know for a fact that the MOT garage didnt pick up a really unwell gaitor on the ball joint rod, many splits in it, could this be the problem?
Only recently started making the sound just as i hit a big puddle in a storm?
Cheers