Here you go.
Create a global variable "Random Timer"
Create 3 separate Events
Condition: On Layout start
Action: Set variable Random Timer to "round(random(a,b))" where A is your min number and B is your max number. This will select a number between the two.
Condition: Every 1 Second
Action: Subtract 1 from Random Timer
Condition: Variable Random Timer <= 0
Action: Do what you want here..
Edit: Added Round Expression. Thank you for pointing that out RamPackWobble