Why ?
Your saw has a brush motor. It's in their nature to be loud and obnoxious and start with a bit of a kick. Part of the price for something simple, powerful and fairly lightweight.
But, there are two main ways to do it if you are determined
Easiest, buy a variable speed unit or a ready built module DESIGNED FOR MOTORS, not a lighting dimmer, and with a minimum power rating of 2kW. It will be described as using "thyristor", "triac" or "SCR" electronics. That will have a knob to control the speed. It will either be a box with a socket you can plug the saw into, or may be a module with simple instructions to follow to wire it in. Turn the knob to slow, start the saw then turn it up to full speed.
You should never use this to run your saw slower than full speed under load but it will let you start the saw with less noise and drama.
More complicated, a high power resistor can be wired in series with the saw that will reduce the voltage / current while the saw starts, with a timer circuit and a contactor to switch it out after a couple of seconds when the saw has started spinning (otherwise the resistor will melt). These aren't an off the shelf device. They have to be made by someone with the electrical knowledge to do so safely so I will skip that, but they do work.
You do not want a so called "VFD". Wrong type of motor to be controlled by one of those.
