What are the causes of my 2 week period that stopped and restarted two times?

Irregular period: An irregularity in your period is likely to be hormonal, that is something caused you to not ovulate this cycle. This could be from stress, excess soy intake or a thyroid issue. Also possible would be a pelvic infection or less likely a polyp or fibroid in the uterus. If this is the first time and you have no pain then you can watch a month and see if it becomes normal.