When two mobile phones are unattended, one mobile phone receives a short message from the other.

If this happens when you use your smartphone.

Then 1 point may think that the mobile phone is poisoned, and an antivirus software is installed for antivirus; Either the mobile phone that sends messages automatically is set to send messages automatically and will send messages at a certain time. Cancel this setting and it will be ok.

If you are not using a smart phone, you can completely rule out the possibility of viruses in your phone. Either automatic message sending is set, or there is an error in the internal program of the mobile phone.