Welcome to the forum. Might be worth having a diagnostic tool to rule out any issues first. Are the vibration through the steering as worn brakes can have effect by or the vcu.
Can you tell approximately where it's coming from?
Is it on acceleration only or even when staying at a steady speed?
Is the speed relevant, ie what gear are you in when it happens?
Is it a high pitched vibration or a throb?
Have you taken it to a decent garage to get it checked out?
A vibration is often very difficult to diagnose when the vehicle is present, let alone over the internet.
I got a vibration after changing the engine mounts to poly. Can't remember what rpm tho.
You didn't answer my earlier questions.
What's wrong with being in 4th at 30?