I’ve had an iMac for around about 10 years now, and over the last week it has had issues booting up.
It will get up to the grey boot up screen, but the pre-loader only manages to make it half up way and then it freezes.
Are there any suggestions on what to do here? Is there anything I can do? Or has it finally given up the ghost?
If it only occasionally does this then run Disk Utility (and then the First said option) first to see if that solves anything, then make a bootable backup to an external drive. (If the problem is the internal drive you can then boot from the external drive and ignore the internal and keep on truckin’.)
Did you try restarting in Safe mode? If that works, once again try running Disk Utility and the First Aid option.
If the Mac simply won’t finish booting it could be the drive or something corrupted in macOS or something in hardware and if you don’t have a bootable USB stick or external drive you’ll likely need a repair shop to look at it.
I second Bowline suggestions, but would not be surprised that the HD is starting to fail. Could you let us know what size and model year your iMac is?
My 2010 iMac runs fine, but the original HD was replaced in 2016 with an SSD and second internal HD (where the CD drive used to be). Well worth doing if you want to save $1.5k.
Thank you all. Much appreciated - will give that all a go …