I don’t know if it also happens to you, but I always have this fear (not only the equipment but also the whole freaking house).
I have two Synology NAS devices and one “custom” server (just a PSU, a Ryzen CPU, two RAM sticks and a SSD).
Everything is grounded, on a compliant safety electrical installation, but I don’t know… I’m maybe paranoiac by nature.
My biggest doubt is about the PSU. It is a certified PSU (from Be Quiet! IIRC), that has more than enough power (500W).
The only stuff I have ever had catch fire in over 20 years if doing this were old crt’s and tv’s. So I just never used to leave those on when leaving the house. I have yet to experience an lcd failure. I have had power supply failures including Apple laptops but they just let the magic smoke out.