Impossible to start my Imac 12,2 Quad-core Intel Core I5

[GregPop]

Hello,

Since 3 days, I try to start my computer, but it never give me more than the boot apple (it started only once over 100 times...)

HID : Legacy Shim 2
busy timeout(0), (60s): 'IOFireWireLocalNode'
and then
IOConsoleUsers: gIOScreenLockState 3, hs 0, bs 0, now 0, sm 0x0
and then
FireWire (OHCI) Licent ID 5901 built-in: no valid selfIDs for more than 3 minutes after bus reset

and nothing...

Thank you for your advise !!!!

 

[GregPop]

For Information, my Imac is running mac os 10.13.6 High Sierra