Recently I started to encounter a new issue with my 3 year old PC. It sometimes turns off randomly, then turns back on after a few seconds. It can happen anytime, even when OS has not booted yet. Sometimes it turns off and on repeatedly, like struggling to keep powered on. Overheating should not be the issue because it has happened right after I turn ir on for the first time that day. Nothing new has been added or installed recently. Also not overclocked.
Could it be a faulty PSU or other hardware?