Hello,
Please note that you can spawn Player Start just like any other actor:
MyPlayerStart = (APlayerStart*)GetWorld()->SpawnActor(APlayerStart::StaticClass(), &Location);
Player Start can be registered in your Game Mode class with AddPlayerStart() function:
AddPlayerStart (APlayerStart * NewPlayerStart)
If you like to learn more about Player Controller in Unreal Engine 4, please go here:
Hope this helped!
Cheers!