Tri-Stage Animation

I want to make an animation that has a beginning “Warming up” phase, a middle phase, and an ending “CoolDown” Phase. it should play the first, loop the second while the trigger (or boolean) is active/true and when it is inactive/false then the ending animation. I’m big into animating but no idea on how the animator works. any help appreciated and if scripting is required please use C#! Thanks in advance!

You can do that very easily in Mecanim.
Here’s official Unity Mecanim tutorial: Unity 4.0 - Mecanim Animation Tutorial - YouTube