Does it matter how fast you crank up your blender?
I opened the first Vitamix manual that came up on an internet search, which is for the Vitamix 5200, available here. It says (on page 11):

Always start the machine with the left switch down in the Variable ( ) position and with the center Variable Speed Dial on 1. Slowly turn the Variable Speed Dial to the desired speed depending on the recipe used. If a recipe calls for processing on High ( ), slowly rotate the Variable Speed Dial to 10 and then push the High/Variable Switch up into the High ( ) position. Do not begin processing on Variable 10 or directly
on the High ( ) setting.

(The spaces in brackets here contain a triangle symbol in the manual).
It also warns not to use the machine for too long at a low setting as this increases the risk of overheating, and not to start on a speed above 1 with hot liquids to avoid the risk of burns.
To answer your questions:

Yes, you should start on a low setting and gradually increase to your desired speed.
No particular rate of progression is suggested.
I would speculate that the analogy with a car isn't quite accurate: for a car the issue is about torque (because the car is heavy and starts stationary) and metal fatigue, whereas for the blender the issue is risk of splattering hot liquid, and (I think) that starting to blend food requires more torque than blending food that is already partially blended. I imagine you could start an empty blender on high speed with no issues, but I don't have evidence to back up that claim.