At idle almost all cards run in passive mode these days (except OEM models with 0,10 € coolers). That has been the case since Kepler era. There could be something that is using the GPU and/or case cooling is really poor.While idling? Sounds like a fan issue. Download a program like HWInfo64 and check if the GPU fans are spinning. At idle, most GPUs are running their fans around 15-20%.
some hours ago it was 50-52 °C now it increased singnifically.why?