IMac is stuck on loading screen

[mta]

Hello

My IMac (2009 i think), was working well, no problems at all. Tonight I started it and is stuck on loading screen. I have tried holding the Shift key and still doesnt stark. What can I do?
This morning it was working fine.

Thanks!

 

[simsaladimbamba]

Have you tried any of these steps?

Mac doesn't boot

Resolve startup issues and perform disk maintenance with Disk Utility and fsck

Troubleshooting: My computer won't turn on

A flashing question mark appears when you start your Mac​

 

[mta]

Thank you!
I had no idea how to use the time machine option. I had to restore the system from a backup.