Can't see HD in disk utility in recovery mode, but can in OS I'm pretty new to Macs.  I got an iMac Pro in 2017 (grey one) and about 6 months ago it started giving me occasional folder flashing icon on startup.

It also started occasionally forgetting my password and so I'd have to reset it.

I figured maybe the HD got corrupted, so I ran first aid on it in disk utility while logged in.  Whenever (after a restart) I run this, it says it's ok.  If I immediately re-run it, it says there's corruption and I must run it from recovery mode.

Problem is, whenever I boot into recovery mode, it can't find the disk at all.

Clearly it can find the disk for me to log in and run disk util in the OS.

I don't have any external drives attached.

It's running Mojave 10.14.3 (I tried updating to 10.14.5 and it has a broken download and won't download the remainder of the update - that's yet another issue).

This iMac has hardly been used at all since I bought it.

Thanks for any pointers.
This sounds like a hardware failure; based on my own experience it will turn catastrophic, and probably sooner rather than later. Hopefully you have AppleCare, but:


get yourself an external hard drive, and make a Time Machine backup immediately.
reset your SMC and reset your NVRAM - if you're lucky, this is just some intermittent / bad state in one of these components and zapping it will restore your mac to full functionality.
take your mac to the Genius Bar and describe the symptoms; hopefully they can replace any defective components, but do this after you have a full Time Machine backup!