@beeman8 I encountered the same problem with 19 inches LG VGA monitors (used with Pi1/2/3). At times the video signal goes blank for a few seconds and then the picture reappears. This can happen anytime while being in emulationstation or playing games regardless of the emulator used. Sometimes the flickering can be very bad (screen going blank every 10 seconds) and sometimes it's milder with the screen going blank only now and then (once every 4-5 minutes).
I spent some time checking up the problem with a signal analyzer and it seems the problem is linked to the quality of the HDMI -> VGA converter used. Some of them (especially the cheapest ones) got very bad DACs that weaken the output video signal to a point where the monitor input got trouble recognizing and locking it as a valid format (hence the on-screen blanking for a few seconds).
When such a problem occurs, there are various workarounds that might be worth trying :
1 - Try to boost up HDMI signal output power from the Pi with the config_hdmi_boost command in config.txt file (explained here : https://www.raspberrypi.org/documentation/configuration/config-txt/video.md)
2 - Trying to boost up the VGA signal output power from the HDMI-> VGA converter by powering the adapter from an external power supply rather than from the video signal input (that is IF the adapter got a +5v input jack socket mounted on which is not the case for all of them)
3 - Replace the HDMI -> VGA converter with a better quality one if none of the workarounds above solved the problem (an idea would be to try several different ones ordering them on amazon so that you can send the non-working ones back at no expense :=)))
Hope this helps !