iMac hanging on startup

[Roladex]

Hi, I'm new to the forums so please forgive me if this has been answered before. I've had a look through earlier threads, but haven't found one dealing with this problem.

My iMac is a 2015 27" running Sierra. I was trying to transfer a file onto a memory stick and, for whatever reason, the process decided to hang. After 10 minutes of the message "Preparing to transfer", I force stopped Finder. When I could not get finder back, I tried to restart the iMac but, after getting the startup chime and the Apple logo, I got a progress bar that stuck on about 60%. I have tried to reboot it several times and it always sticks at the same point. This includes starting in recovery mode (holding the alt key) and resetting the NVRAM. The hard disk is rumbling so something is going on but the progress bar remains stuck on 60%, even after around 30 minutes.

Do I leave it alone and it will start eventually or do I need to take some other action?

Thanks in advance.

 

[Roladex]

Solved

It seems all it needed was time! Although it took over half an hour, and just as I was about to despair, my home screen suddenly appeared!

Apologies for the false alarm.

 

[chscag]

Not a false alarm. Your 2015 iMac may have a fusion drive installed which are known for being "cranky". You might want to boot to Recovery (command plus r) and run Disk Utility First Aid on your Macintosh HD just to make sure there are no errors.

And welcome to our forums.

 

[Roladex]

Thanks for the welcome chscag! I'm a bit ashamed to say, I may have contributed to the bootup problem: I'd left the thumb drive in the iMac when I rebooted. I thought it was blank, but there must have been something in there conflicting with startup. I took it out and - boom! - I was back. Still not sure what happened as Finder showed the drive to be blank before I used it....