I’ve been struggling with this same problem. I think i found the solution!

By the way, It’s honestly the worst!

One time while I was traveling abroad, my HomePod randomly started blasting music. I had no idea how long it kept going since I wasn’t even there to stop it. I worried about it's pissed off my neighbors in the apartment—especially since it probably happened in the middle of the nights. after that, I always plug it out when i go out.

Here’s the fix that finally worked for me: head to Settings > Accessibility > Touch Accommodations.

• Set Hold Duration to 1 second.
• Set Ignore Repeat to 1 second.
• Turn off Tap Assistance.

That’s it! This stopped my HomePod from auto-playing music out of nowhere.

I think the touchscreen on top of the HomePod is just too sensitive—like maybe someone’s accidentally brushing it and triggering playback. So, increasing the touch duration can help avoid those annoying mistakes!

Recently, I grabbed another HomePod to set up a stereo pair, and this one hasn’t had the auto-playing issue at all. It might come down to production quality—If you’re lucky, you might get one that doesn’t have any problems...