This condition may not be a mental illness but a psychological phenomenon called "song thinking" or "musical thinking." Many people feel this way, especially when they feel relaxed, happy, or excited. Some people would find themselves suddenly humming a song or playing a song in their hearts. This phenomenon may be due to the brain producing a "creative" response when processing information. When we feel happy or excited, our brains release neurotransmitter like Dopamine, which causes our mental state to become happy and excited. In this state of mind, our brain may begin to produce some "by-products" that process and code the feelings of pleasure and excitement into a form of music, such as singing or playing music. Although this phenomenon does not necessarily lead to disease, it may affect our quality of life. Therefore, if you feel troubled or troubled, you can try to take some measures to reduce the impact of this situation, such as trying to meditate or deep breathing exercises, or through other means to reduce the level of neurotransmitter released by the brain.