Hi and Welcome,
As we are unaware of the exact model of your phone and what you may have actioned already, here is some general advice.
Ensure your on the latest software and check for updates.
You could Soft Reset it as a First step. {Turn off, battery pull, if removable,and turn back on}
As a Second step you could perform a Hard Reset but please make a back up first as this procedure typically deletes saved data.
Find out how to do this by googling , How to hard reset a Sony Ericsson {then your model of phone}.
Good luck.
