Have someone test your plug with a tester that goes into the plug and checks if it has an earth leakage etc. This can cause the issue that you mention intermittently. Doubt a 2 GPU rig will draw so much power as to trip a circuit breaker or a fuse.
If the plug is perfect it could be a faulty PSU.

The mobo image appearing can be set in the BIOS to display or not. nothing to do with the power issue.

Just test the rig in another room in the house and see if it does the same.