When planning on driving to Positano or Amalfi Coast, one should remember that there are two ways to get there:  around or over.  Usually the quickest way is over, take the high road from the other side of the peninsula.  There are a couple of things to take into consideration.  These are TINY mountain switchback roads with steep rocky cliffs, and the smaller your car is, the easier the drive.  Think Fiat 500 rather than Land Rover.  You will have to pass buses, pedestrians, scooters and oncoming traffic on tiny roads with hairpin turns and there is often road repair going on and one way traffic lights, etc.  If you don't like stressful driving, DON'T drive to Positano or Amalfi Coast and definitely DON'T drive the road at night.

Private drivers is a nice alternative, and as follow companies based in Positano.