Mac book pro rebooting then shutting down

Question

Everytime I turn my MAC book pro 13 inch laptop on, it takes me to the white screen with the grey apple logo and then starts to reboot. I'm not entirely sure of it's rebooting but something is loading and the background colour is white if that helps.
Once it's about a quarter of the way through loading it starts showing a loading sign and the bar that's only a quarter of the way filled disappears. Then the screen turns black and it shuts down. Every time I turn my laptop on this happens. Please help.

Answer 1

Megan.west,
if you have Mac OS X 10.7 or newer installed, you can try this: boot your MacBook Pro into Recovery mode by holding down a Command key and the R key as it starts up. Once the Mac OS X Utilities menu appears, select Disk Utility. On the left-hand side of the Disk Utility window, select your internal disk’s boot partition (typically called “Macintosh HD”). On the right-hand side, select the First Aid tab if it’s not already selected, then press the Verify Disk button if it’s not greyed out; if it is greyed out, or if it reports that errors were found, press the Repair Disk button. Once the verification/repair is completed, exit Disk Utility and select Restart from the Apple menu to restart in normal mode. Does it get past the white screen and progress bar now?