There is no fan belt on the VQ35 as such.
There are two belts, the main serpentine belt and the aircon belt, and both are adjustable.
If the starter motor is only sticking then a clean will fix it, but if it is an internal electrical fault within the starter then a replacement starter will be required, or it may be a faulty starter motor soleniod which is part of the starter motor.
A new starter motor from Nissan is £420.40.
I have preowned starter motors available at £125.00.
Also check that the ignition switch is not sticking.
Alex.
cheers alex