it is often the PSU, but it can have also different reasons ( there is other hardware in your PC ).
But most common is the PSU. In generall there are huge differences in PSU quality and enginering and the value of 550W say not much.
More important are this values from manual:
I would assume it should works with that PSU, but it is border-line for me. And a PSU can also be faulty or we had some cases where the cables are lose 