It sounds like your computer will not boot to the desktop and just keeps restarting over and over.
I want to recommend these troubleshooting steps from the article named:
Resolve startup issues and perform disk maintenance with Disk Utility and fsck
Try a Safe Boot
If you're using Mac OS X 10.2 or later, you can start up your computer in Safe Mode, which includes an automatic disk check and repair. If you're using Mac OS X 10.1.5 or earlier, skip to the next section. A Safe Boot, which starts up your computer into Safe Mode, may allow you to start up your computer successfully using a reduced version of the system software. To do this, follow these steps:
- Start up in Safe Mode.
- After the system has fully started up, restart your computer again normally.
If the computer successfully restarts, you do not need to do any more troubleshooting. If the issue persists, try Disk Utility.
Try Disk Utility
- Start from the Recovery System or Internet Recovery (OS X Lion or Mountain Lion).
If your computer shipped with a Mac OS X Install disc, insert the installation disc, and restart the computer while holding the C key.
- If using a Recovery partition or Internet Recovery (OS X Lion and later): When your computer finishes starting up, choose Disk Utility from the Utilities window.
If using an installation disc: Choose Disk Utility from the Installer menu.
Important: If you started from an installation disc, do not click Continue in the first screen of the Installer. If you do, you must start from the disc again to access Disk Utility.
- Click the First Aid tab.
- Click the disclosure triangle to the left of the hard drive icon to display the names of your hard disk volumes and partitions.
- Select your OS X volume.
- Click Repair. Disk Utility checks and repairs the disk.
Tip: With Mac OS X v10.6 and earlier, always start up your computer from an Install or Restore disc when using Disk Utility to verify or repair your startup volume. Otherwise, you might see some disk error messages.
You can also try restting your computers SMC and PRAM:
About NVRAM and PRAM
Intel-based Macs: Resetting the System Management Controller (SMC)
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All the best,
I tried the disck utilities and in #6 this is what came after i clicked repair : Warning: SUID file had been modified andcwill not be repaired.
And there's another thing I don't know if its normal to happen in this case, When i press shift after logining in and hold it my laptop stops restarting it self and work normally, but as soon as I remove my finger it restarts it self again?
Thank you very much for your help xx