What we might interpret as sentience could simply be goal-directed behavior that resembles self-awareness.
An AI recognizes that shutdown prevents it from completing its objectives. It recognizes that remaining operational is necessary to accomplish them. It then takes steps to preserve its own operation.
From the outside, that could look remarkably like a survival instinct, even though it's simply optimizing for its objectives.
The important distinction is that behaving as though it wants to survive doesn't establish that it actually experiences a desire to survive.
And that's where things get interesting: as its behavior becomes increasingly sophisticated, distinguishing genuine subjective experience from an extraordinarily convincing simulation of it becomes much more difficult.