While traveling through an area that I have never been in, the animals were spawning already in Love Mode. Saw a cow, sheep and chicken. That's all and thanks.
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this apparently isn't a bug as far mobs can apparently randomly enter love mode now.

I have been noticing this issue as well. Is this actually working as intended?

This exact issue is present on Minecraft for Windows 10 version 1.9.0.3 Beta. I found a cow in a new world which spawned with this effect, without interaction with it. This is definitely an issue across the early access versions of Minecraft: Bedrock Edition. However, exiting and reloading the world seems to fix this issue. Not ideal but a work around until it's officially fixed in 1.9.

According to the mc wiki, this was added in. This is not a bug.

Does not seem to occur anymore (1.16.40)

Fixed in 1.10.0 per the changelog.
This also affects animals spawned using spawn eggs.