The paradox starts with the sending back of the T-800 to kill Sarah Connor and Kyle Reese to protect Sarah. But keep in mind that a timeline occured where only the T-800 existed first. Assuming events unfolded similarly to the first film, the T-800's presence would not have actually changed the timeline much, as it believed Sarah Connor dead after it murdered Ginger. In the timeline where Kyle and the Terminator exist, because Kyle had followed Sarah, Sarah called Ginger after her murder.