How to add a smooth transition up into a rotation?

Hi, I have a script I use to make an object slowly rotate that I enable with a trigger. It works great, but when I trigger it, it jumps into the motion very suddenly/not smooth. So I’d like it to slowly ramp up into the rotation.

This is the code I am using:

#pragmastrict

functionUpdate() {

transform.Rotate(Vector3.up * -10 * Time.deltaTime, Space.World);
}

Oh this looks interesting, but I’m too new to coding to fully understand it…is that idea that I’d add SmoothStep inside of the transform.Rotate? And that slows it down initially?