This is the default Bootstrap Behavior of Collapse.
Mainly this is managed by the class "collapse in" and collapse"
If you add the "in" to the related DIV Collapse Body class, it'll be expanded on load.
What you can do is edit the Accordion Cell in Toolset Layouts (not the single Accordion Collapsible Item, but the entire Cell).
There you will see an option to add an ID.
Later you can remove the "in" class from all occurrences within that parent DIV.
That's easy with JS:
//Replace "contains" with the ID you gave to your Accordion Cell in Toolset Layouts
Please ignore the previous one, this will not work and there is much a simpler approach.
Just create your Accordion cell as used to.
No need to add any ID anywhere.
Then add this to the JS Section of Toolset JS/CSS:
Load the Fron End, now you should see all accordions closed, and on click, each accordion should properly expand.
What we do with the code above is targeting every accordion body produced and remove the "in" class.
Since Toolset Layouts automatically generates the ID with a random number I used a wildcard to address the hardcoded Toolset Layouts Accordion body prefix: