The warmth you feel while using your phone for an extended period of time is primarily due to the internal components and processes involved in its operation. Electronic devices generate heat as a byproduct of their normal functioning.
When you use your phone, various processes such as data processing, network connectivity, and screen activity require the device's components to work, which generates heat. Additionally, factors like battery usage and the power drawn by the processor contribute to the overall heat generation.
The warmth you perceive is generally not a cause for concern. However, if your phone becomes excessively hot, to the point where it's uncomfortable to hold or it affects the phone's performance, it could indicate an issue. In such cases, it's advisable to contact the manufacturer or seek technical assistance to address the problem.
It's worth noting that the radiation emitted by your phone, specifically electromagnetic radiation in the form of radio waves, is generally considered safe and regulated by international safety standards. The warmth you feel is unrelated to this type of radiation.