If your device turns on or off by itself, kindly check if your device is in any of the situations below.
1. Please check if you have shared the device with other users. Other users can turn on/off the device you shared. No need to anything in this case.
2. Please check if you have created any timers or scenes to trigger on/off the device. Delete the scene or timer when you don't need the device to auto turn on or off.
When neither of the above method works, delete your device from your account and add it again. Check if the model auto turns on/off by itself.
If the problem persists, please contact the seller for further help.