My problem is solved, but I don't know why, so I'm reaching out because I'm curious.

I installed a Kenwood Excelon DDX9905 about a year and a half ago along with the OEM Audio+ Reference 500 system (Speakers, sub, amp/signal processor). After install I would intermittently get only white noise when I'd start the ignition. The unit would power up, look like it was playing music, but I'd only get static. I'd power down the head unit while driving. It would take a few seconds after power down for the static to stop. If I immediately turned it back on, I'd usually still get static. Conversely, If I left it off for 5+ minutes and restarted it, It would work fine. I rechecked my ground to no avail. It was moderately annoying but I never got around to taking it into my car stereo shop. Fast forward to a few weeks ago, my stock battery was dead. I replaced it with a X2Power Premium AGM BCI Group 24 Battery. Since then I have had ZERO instances of static.

Does anyone have an understanding of what was happening / why it works now? Just curious.