Hello @Steveymac and welcome to the community!
Start by testing other wall chargers or USB cords, or mix between them, and check if you get the same issue.
If the issue still persists try restarting your phone into safe mode (use the blue link for a guide). This will temporarily disable all 3rd party apps, so if the issue disappeared this will hint that one of your apps is acting up and you'll need to figure out which one, or simply perform a software repair using Xperia Companion.
This will do a clean installation of the latest firmware and will also wipe your internal memory. Don't forget to backup using Xperia Companion, but preferably without adding apps or settings to the backup.
Follow the steps given in blue links, and keep us updated.
