Samsung galaxy S4 problem

[Fifi__]

Mobile fully charged. When I start using it screen disappears and samsung logo comes up. After a couple of seconds the screensaver comes up again. Frustrating as you can't read an email, text or browse online

 

[hang-the-9]

Try a factory reset, that will set everything to defaults but will wipe the phone, so make sure your stuff is backed up or stored in cloud storage or SD card.