Hi,
Download, install and run Malwarebytes Anti Malware Mobiles. It will detect and remove any malware that has been installed on your phone.
Here is a link.
https://play.google.com/store/apps/details?id=org.malwarebytes.antimalware&hl=en
Download, install and run Avast Mobile Security and Anti Virus. It will remove any viruses that are on your phone.
Here is a link.
https://play.google.com/store/apps/details?id=com.avast.android.mobilesecurity&hl=en
Hopefully between the two of them they will remove the cause of your problem.
If it still happening after you have run both of the above, you could try uninstalling the most recently installed apps on your phone, one at a time and see if the problem disappears. As a last resort, perhaps a factory reset is the answer. Be aware doing this will erase all your user data and downloaded apps.