How to setting up shuffle duration for a list of repeated items

Hello Community,

I have a list of repeated item from database, SLICE() the repeated items to 4 to show up 4 at a time using SLICE(data.items, 0, 4) from the first document with default index “0”. Lets say my DB contains 100 items and I want to SHUFFLE() my database items and slice it to 4 then show up the new shuffled 4 item for duration of 30 seconds. Try with ADD_DURATION(NOW(), 30, "seconds") and fails. What I want to do is it keep shuffling to new 4 repeated items from the DB whenever the page is focused.

When I using this formula SLICE(SHUFFLE(data.items), 0, 4) it keep shuffling continuously without even time to load the content in the item.

How could be possible??