Great thank you Hooker47 and Heliaviator and others for your replies that was what I was after.
Incidentaly Hooker47 I have had partial light offs in a engine (s76) which can be interpreted as vibrations however nothing like rotor/shaft unbalance. I guess it depends on how one defines vibrations. As you said though crossfeeding for the start and priming the engine solves the problem quickly if it does not just stop itself.
From the Authors perspective he may have heard the pilot wrong or just remembered it wrong. I just wanted to check.
Cheers
P.S
I really enjoyed the book. Although it was not writen that well. It was still a good informative read. If you like that type of book I would recommend it.