I searched with Google for "when to capitalize google" and this article was the 4th result. The author cites the AP style guide, the Chicago Manual of style (which was the 3rd result), and Merriam-Webster.
The style guides agree that there is not a set rule for capitalizing 'Google' when used as a verb. They suggest capitalizing it since it is a trademarked name, but they're not going to come after you with torches and pitchforks if you don't.
Google's own style guide (result #5) provides this rule and clarification:
Don't use as a verb or gerund. Instead, use search with Google.
In short, Google says to always capitalize it but just use it as a proper noun. The style guides recommend checking with the people giving you your paycheck/grade and follow their guidance.