Create New String with Several Random New Line

I have a string:

String text = "Nothing right in my brain. Nothing left in my brain"

I want to create a new string text2 that has 2-4 random new line from previous, such as:

"Nothing \n right \n in my brain.  \n Nothing left in my brain"

or

"Nothing right in \n my brain. Nothing left in \n my brain"

How to create a new string with random new line between the words? I am thinking to get the index of whitespace, in order to insert new line after random whitespace. But I only keep getting the first whitespace index. Anyone know better approach to solve this? Thank you.