You will need to set the timer every time you want to change the time so you should probably not be looping but set a new timer every time the old one is done.
I noticed that if you check looping it keeps only first result. How do I make it has to wait random amount of time each loop?
For example this is part where is spawn actors:
I do it all the time but not a looped.
you can do some function like callMyEventAtRandomTime and inside you use set timer by function name , no looped and in time just plug a random float in range with your desired min max random values.
inside your looped event, when it ends and is about to leave just call callMyEventAtRandomTime function again to self invoke it at a new random delay