both google and youtube give out me neofur or random hair simulation video…
Can the engine simulate hair itself without any addons? And how?
Depends on what you mean with simulate 
The UE4 offers a special hair shading mode: https://docs.unrealengine/latest/INT/Resources/Showcases/PhotorealisticCharacter/?utm_source=launcher&utm_medium=ue&utm_campaign=uelearn#hairshading but for movement you will have to use APEX or you have to implement the movement as an animation
I googled APEX but what I found doesn’t have anything to do with simulating hair.
Edit : nevermind, I found it : https://docs.unrealengine/latest/INT/Engine/Physics/Apex/
APEX is actually used for cloth simulation, but you can also use it for hair to get movement 
It’s a standalone application and a plugin for 3ds /maya