It does not even matter what you start arguing over, what you are getting down to is who is the boss and who is not. If you have to win every argument you will probably lose your marriage. That is something to think about. If you always have to win, chances are you will lose your marriage. If it is a source of chronic disagreement, you have a real problem.
Sexual difficulties can be all sorts.
They can be from what type of sex you want to do, to how frequently you want to do it. In fact, frequency of sex is at times a source of conflict in a marriage. And that at times in itself becomes a sexual difficulty. It is nice if you can talk to your partner up front concerning this. Positions, experimentation, fantasy.