Make a float variable by the name of TimeSinceInteract and a bool variable called HasInteracted. In each of your input event nodes, set HasInteracted to true. For your Tick node, check if HasInteracted == true. If it is true, that means…well, the player just interacted! Set TimeSinceInteract to 0 and set HasInteracted to false. This in effect resets our counter and turns HasInteracted back off (if we didn’t do this, then if they pressed a button once, we’d keep thinking they pressed it every frame!)
If HasInteracted ISN’T true, then add the Tick’s DeltaTime to TimeSinceInteract.
After this adding bit, check if TimeSinceInteract >= [however long the idle time is]. If so, then change the level to the main menu.