So you want to create an actual autosave system that autosaves every x time? Or do you mean as a prevention mention, to prevent the player from saving the game again, if they have recently saved already?
If it's the prevention measure then...
1. create a condition 'can_save' & set to false or true as default (whatever you need it to be).
2. wrap the autosave actions inside of an if query.
if condition 'can_save' is true
execute autosave #?
3. create a called by other action & name it prevent_save
. Inside of this action add these action parts...
change condition 'can_save' to false
pause for x time
change condition 'can_save' to true
4. inside of actions where you execute the autosave, create a call action 'prevent_save' immediately after executing the autosave.
That should about sort it out methinks.