Here is a quickest, easiest example I could think of.
I created a bool called “Game Over” and on begin play, I set a looping timer and save its handle.
The timer keeps calling the “Keep Spawning” event every 1 second (Timer Time - gives you control of how fast to spawn objects). The event is spawning the object at a random point inside a bounding box around your ship (Or any object you want, you will need reference to), then finally checks if the game is over and clears the timer if it is.
You could also call clear timer from somewhere else in your logic that determines when the game is actually over, that way you do no have to check on every timer event call.
