Temporary black screen Samsung galaxy tab A

Hi all, thanks in advance.

My daughters Samsung galaxy tab A's display keeps blacking out. It happens most often when she's playing games but also when just operating the tablet. It's not the screen blackout problem were you can't see anything and have to reset. It's just temporary, she moves the tablet and it comes back. It's like it is going into power saving mode but it does it every 30s or so and even when it is being used. I've reset the tablet, checked the power and display settings and I can't see any reason for this to be happening.

Advice please?