screen goes black for several moments ...

This is a really worrisome problem:

Just upgraded from Win7 pro x64 to Win 10 Pro. At the same time I replaced the motherboard, ram, video card and added an SDD.

I had this done by a computer shop that I trust. The tech spent some time replacing and troubleshooting drivers.
I have had the computer back for about a week. Aside from the odd bit of fuss with legacy programs and me learning the ins and outs of Win 10, it has been pretty smooth.

Yesterday, while browsing the 'net, my screen suddenly went black and the monitor turned off (or at least the power on button lost its light for a fraction of a second). The screen stayed black for several moments...less than 30 seconds maybe less than 10 seconds. And the ASUS logo displayed.

Then the screen came back on...for a couple of moments and went black again. This repeated about three or four times.

No more problems the rest of the day even with a round of Skyrim for several hours.

Today I have been experiencing the same problems off and on with repetitions of as much as 8-10 times. Usually while browsing or checking email or...inconsequential stuff, really. This went on every so often most of the morning and then no problems again despite three hours of gaming until the early evening when the screen went black five times in a row over the space of about 1-2 minutes. No further problems so far.

Throughout all this, when the monitor comes back on the desktop is just as it was--no loss of data.

I could really use some help or advice with this I am very worried.

i7-4770k, 16 GB ram, XFX Radeon RX580, 620watt PSU, Windows 10 version 1903, build 18362.418

PS...have checked connections, everything seems tight.

Check Reliability history (click Start and type reliability...). It will probably show graphic card errors...
In that case reinstall drivers for graphic card, but I would first download chipset drivers from MB manufacturer (from Intel site would be fine too).

But post the picture of reliability history first

Click on each of the red Xes, what do they show in the Reliability details?

Could you still post. Could be a symptom. Especially second line down, Window failures?

Did shop do anything to prove / burn in Video card? Could be something as simple as faulty new card.

DWFII said:

Every single one of them read as in the pic above--"Windows was not properly shut down."

But that's another issue and there's no apparent ill effect--none correlate time or date-wise to the black screens and I never instigated nor noticed a shut-down at the times specified in the red warnings.

I would like to see description of marked events. Application and Windows errors.

Would be good to proceed with basic troubleshooting: sfc /scannow, checkdisk, etc. But first, if you could please check marked events