[Troubleshooting] Sudden Runtime Broker CPU usage spikes causing frame drops

I first started noticing this today: I'll be playing Beat Saber, then frames start getting dropped. When I check why, it's CPU usage spikes bloating the frame time, and Task Manager lists "Runtime Broker" as using the most CPU for a few moments. If I wait a bit it'll go back to not using CPU and I can continue normally. I'm not aware of updating anything recently.

I did already find this thread which suggested disabling showing tips about Windows, but despite only leaving "Get notifications from apps and other senders" enabled, the problem persists.

It looks like Runtime Broker has to do with launching UWP apps, and while I do have some installed, it doesn't occur to me why they'd be launching in the middle of gameplay.

Has anyone else had this problem? Any suggestions for things to check next?

I'm using:

• Windows 10 Home 1809 build 17763.195
• SteamVR 1.1.4
• Beat Saber v0.12.2
• NVIDIA drivers 417.35
• Ryzen 7 1700 8-core CPU
• 24 GiB RAM
• NVIDIA GeForce GTX 1080

EDIT: Looks like the disruptions are approximately - but not exactly - every 15 minutes. So something's scheduled, but I don't know what. Hopefully I can find it.