Random TP

Hi! Im trying to make a datapack where every 5-30 minutes, I get randomly teleported within the border of 650x650... I used spreadplayers when I was trying to do this myself because Id rather not be teleported in the sky or in the ground... Anyways, Im also trying to add a counter that says 321 TELEPORTING! on the screen using /title in a green text... and I need to account for the fact that the nether is smaller tan the overworld so if im in the nether i need to be making the teleportation radius smaller so that I dont go out of the worldborder... ive been trying to make this datapack for days and I always run into one issue or another. thank you in advance.