The "hooding" sounds like possibly a harmless escaped Hognose Snake (Genus Heterodon) that belonged to someone. Impossible to say without seeing a photo though. These snakes can be EXTREMELY variable in coloration and/or pattern. Other snakes such as the native Pacific Gophers can inflate their necks laterally and flatten their heads, but not really wide horizontally like the Hognose Snake can.

However, without knowing what it actually is, I'd recommend due caution. Here is an example of an Eastern Hognose doing their typical defensive posture hood flaring.

cheers, ~Doug

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"a snake in the grass is a GOOD thing"

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