This is a difficult one. You don't mention over what time period these 4 jobs occurred over but if they all are within, say a year or even two....you are in a tough place. Normally I'd advise to NEVER bring up negatives about yourself or your performance during an interview but in this situation I'd almost take the bull by the horns and address your employment history.
For instance you could say, "I know that my work history has been sketchy but my brother in law had a terminal illness and I left work a couple of times to take care of him until he died." (or whatever your real reason is). If you've been recently divorced, widowed, separated, suffered the death of a parent or other major personal problem, and left work to deal with all of the details....that stuff happens and nurse managers know it and may cut you some slack.
Now.....if the real reason you left is that you couldn't get along with your manager or you couldn't get out of bed and were habitually late
...this will take more talking. In that case you might want to say something like you've have been trying to find your "niche" in nursing without success and then tell the Nurse Manager why you think the potential job is a good fit for your skills and interests.
Put yourself if her shoes and realize that she doesn't want to commit the time and money to train you if you will be walking out the door in two months. Your challenge during this interview is to convince her that whatever caused you to leave before is over and that you are committed to the new job.
Good luck and let us know how it goes!