Recently purchased an 06 SS with the 5.3 and occasionally upon initial start up it throws a message of low oil pressure turn off engine ?
turn the car off let it sit for a min , fire it back up seems to be good? Checked oil level and it’s good , could it be a sending unit& where is that located?

 

With the 3800s, its almost always the sending unit. With the LS4 like you have, its a common reason but not the only possible one.

The sensor is on top of the engine just behind the throttle body (youll see where the intake manifold is notched in to allow space for it). They're cheap and easy to replace so its a good starting point.