Short of having access to an oscilloscope to look at exactly what is happening on the supply rails, you have two other options:
1- hope that the Anti-Surge warnings are false positives and disable Anti-Surge in the BIOS
2- try a different PSU of adequate power rating and decent quality. Since you currently have no GPU, you could easily make-do with something like an Antec VP450 which you should be able to find for $40, possibly less
Or possibly three:
3- try disabling CPU C6 state somewhere under the Power options if it is still enabled. Since you have no GPU to help load the PSU down, the PSU might be having a hard time with transients under very light load. You actually might want to try this first.