Tab A keeps switching off especially when first using it . I need to keep turning it over to get the screen on. After a few minutes it seems to work better as if it needs to moved a lot or warms up? It's done this since New but every time I returned it the car motion seemed to get it working!
You said "every time you returned it", so you did exchanged it already? Need some exact details about what is happening, does it fully shut off or just the screen? You may want to some someone locally look at it to check the settings to make sure it's not just turning off the screen for powersaving which is normal.