I cannot remember somebody reporting this problem here in the forum - you might be the first. It sounds like a hardware issue. You could disassemble the cover and have a look at the vibration motor at the back of the phone. here is a description of its position:
That even works while the phone is on and you could initiate an event where the phone would usually vibrate to see what happens to the vibration motor.
Yeah that’s due to the mass of e-mail support requests. You could call them - this usually works a lot faster.