This has only been going on today.
Additional context: When the ping spikes happen, I don't just have slower inputs; the game itself actually skips forward in time, meaning I actually miss anything that happens within the one second or so of time that the ping spike takes.
I generally sit at 16-17 ping, but today it has been jumping up intermittently to 200-300+ in addition to making me miss a second of time. Whatever happens in that second is lost, but delayed sound effects will play after ping returns to normal.
It's only been happening today.