Greetings,
Already using dual PCIe.. Sorry, missed that. New PSU is probably fine.
Rebooting can fix all kinds of subtle problems. The issue could be related to RGB software, voltage or maybe due to heat.
I wouldn't worry about it too much if temps, voltage and performance appear normal. Maybe watch it over the next few days/weeks and see what precipitates the behavior. Happens over time, after you play X hard, when the machine goes to sleep and wakes. Or when it exceeds a certain temperature threshold (example). Yo'll have to watch it and see if there is something specific that causes it.