Becoming Aggressive, Sometimes Tired, Recovers From Depression. Want Opinion

Hello Doctor. This is regarding the health of my mother, who is 84 yrears. Past one year, she seems to get aggressive for one or two days in a month. She keeps yelling at everyone, saying they have all her belongings. Keeps packing her bags and tries to go out. We have to retain her forcibly. But after a day or two she looks very tired and seems like recovered from a major depression and becomes normal. We doubt it is some sort of sickness and would like to have your opinion in this regard pls..