Resets are common on this system. There is loads of literature on it. Some will say it's bridge rectifiers but more than likely its a case of reseating the short ribbon connector or replacing it or try reseating J114 on the power board. This can can oxidise over time and reseating it can remove it. Ultimately it's the beginning if something failing.
There's also a wonder device you can plug in to stop the resets but ultimately you're only masking a problem.