Try running system diagnostics to rule out a hardware problem. Restart the system and at the Dell splash screen start tapping F12. Run full diagnostics watching for a hardware problem.

Also

https://www.dell.com/support/article/us/en/19/sln129591/system-locks-up-freezes-or-an-error-occurs?lang=en

I have exactly the same problem, with the same model. 

1. Please check your CPU
2. Change the system
3. Graphics card problem
4. The problem of the motherboard itself

Amr Soft - 1 Coppper - did you ever resolve your issue?  I have the same set of symptoms.  Had Dell's tech support work on it three times - no success.  Now awaiting tech support's review of files.  I'm not optimistic.  My problems began shortly after I upgraded to the most current BiOS in August 2019...prior to that I was OK.  There seems to be LOTS of adverse chatter about the current BiOS overheating, etc.  But I don't know whether those complaints are germane to my set of issues.  Still...I don't believe in coincidences.

I do know that re-installing the current BiOS seems to eliminate the issue, but only for a short period of time (an unpredictable period of time lasting anywhere from 10 minutes to 4 hours, depending apparently on how I hold my tongue in my mouth).  Joking aside, this problem is fatal if not corrected.  I don't like having a G5 paperweight on my desk.

Seems the vast majority of the issues are with the G5 series - with Intel i7 chip and SSD - I don't see complaints about the XPS or Inspiron laptops.  Wonder if its a G5 machine issue, an Intel i7 issue, a G5 BiOS issue, or some combination of the above?  In any event the issue is shared broadly enough for me to conclude it is a Dell G5-wide issue.  So I'm displeased Dell isn't (a) acknowledging the problem and then either (b) launching the proper fix or at least (c) letting us users know the cavalry is coming. 

Sometimes, confession is good for both one's soul and also one's reputation. 

I'm having the same issue sporadically. My G5 5590 with 512GB Toshiba SSD (m.2) does this when the CPU is on 100% load.

- G5 5590 with 512GB Toshiba SSD, 16GB DDR4 memory (single channel), Nvidia RTX2060.
- Windows 10 1903 with latest updates.
- Nvidia driver 440.97 (happened with previous versions as well).
- Latest UEFI Firmware ("BIOS") 1.1.0.0
- Thermal Management set to "Maximum Performance" a.k.a. Jumbo Jet Noise Mode.
- Hyper Threading turned off, only using 6 physical cores.

ok i cannot even get in to do anything  with it  it stuck at the lock screen 

is there a shut down somewhere on the laptop ?

I have the exact same issue on the same model.  Incredibly frustrating - I can't get any work done.  Has anyone been able to solve the issue?