A critical part of your narrative is that you have identified things that trigger her behavior. What are they? Is there a common thread? That may give you a clue to what is going on with her. Mood swings may indicate a medical problem. Note that she has been married three times before. Why did those marriages end? How long did they last? Answers to these questions may open the door to a conversation with her. It is admirable that you want to look out for the children's interests. How does she feel about that?
Thank you for your response and insight. Upon further reflection, the triggers to these outbursts seem to lie in areas of contention that she has with me ie. my job and its demands. (I work in retail to supplement our income and this calls for weekend day shifts which takes me away from the home during the weekend, leaving her feeling isolated and lonely. She has expressed this to me in those words.)
My wife's previous marriages ended, I fear, because of her behaviors within the marriages, behaviors I believe to be akin to those she exhibits with me. She is a product of a divorced family herself, and in so, does have insecurities about relationships. An almost fatalistic view, that all relationships fail or end and someone ends up leaving. This is reflective of what occurred with her parents, both of whom, abandoned her at some point or another during her formative years. Her previous marriages did not last long, all less than four or so years. Our marriages have outlasted all of her previous marriages combined. Unfotunately she is very opinionated, and in so is not open to discussion on subjects she does not hold the upper hand in. If I parrot back something she may have said at one time or another when applicable in a discussion, she will essentially shut down and not entertain any further discussion. She has a tendency to read to take things out of context, marrying two sentences together or giving her own spin on something that was said, when in fact the inference was not ever there. I hope this gives some further insight for you to some further thoughts.
Thank you for more information. If she is feeling isolated on the weekends, is there something she could do with the kids or some other recreational interest with some friends? It seems that your spouse needs to find some insight into her own history regarding marriage and her inclination to end them. Certainly some marriage counseling would help if she is willing. It seems that she may be locked into a pattern that she is unaware that she is creating. Communication is a two way street and essential to keeping marriages intact.