Hi!
Could be caused by multiple things. At first, this does sound like a problem with the PSU, but could also be caused by the CPU/GPU.
I would replace the PSU first and test if this is the solution or not (big chance this will fix it).
Guide: [guide|141729|PlayStation 5 Power Supply Replacement - iFixit Repair Guide|new_window=true]
If you need anything else, please let us know!
Good luck!