You submit your book and you now you play the waiting game with KDP. What is suppose to be 72 hours for a book to be reviewed, can now be around 10 days in a lot of cases.
You check one day and look at your bookshelf and your book is back in draft mode after being in review for many days, should you just re-submit it?
The answer is NO! This means KDP has kicked your book back for a reason and will let you know what it is. Check your email for an email from them and the reason. The email can come a few hours after they have kicked it back. So do not re-submit it, until you see the email and fix the issue.
Continuing to re-submit your book, without fixing it, could lead to being suspended or worse. As they have the expectation that you will check email, read it, fix the issue and re-submit the book all within a timely manner.