Your children have had a temperature of 37 without symptoms? They do …

Your children have had a temperature of 37 without symptoms? They do this almost every month, I just take and check with a thermometer and it shows sometimes 37, and sometimes 36.5. Although the child is not hot and behaves as usual. It has been going on for several days and I'm already giving up on it. We went to the doctor, they don't know why. They wanted to give them an injection, but how can you give one if there is a fever? The thermometer works, I hold it for at least 6 minutes, and maximum 10. Maybe someone has encountered this? We think about teeth, but she is not bothered and behaves as usual.