My Mac is stuck on apple loading bar screen.

I have the exact same problem.

I tried holding p+r+command+option (nvram/pvram) while powering on the computer: loading bar appeared, never completed because screen went black.

I held command and r : did first aid with no results

command and r again: reinstalled OS successfully but problem persists.

held d (some hardware diagnostic): it found no issues.

If I restart without pressing anything, the loading bar ALWAYS gets stuck after progressing about 1/3 of the way and then the screen goes black, but I can still hear the computer running.

I am only able to successfully start the computer if I hold shift (safe mode?) upon boot up when I hear the chime. And when it boots, everything is very delayed/laggy. Please help.

Also, I have a 2017 iMac.

Thanks

If your Mac is still stuck on the loading bar screen after trying NVRAM reset, disk aid repair, reinstalling macOS, and erasing all your data, it may indicate a hardware issue. In this case, I would recommend taking your Mac to an Apple Store for further diagnostics and repair.

I‘ve included an article for you to read if your Mac starts up to an Apple logo or progress bar.

If your Mac starts up to an Apple logo or progress bar - Apple Support

It's not normal for a machine in good shape to act like this, and I understand why you're feeling annoyed.

At this point, it may be worthwhile to consider going to an Apple Store.