acastelein's Identifications

Saw it lying across the trail, but when I got close with the camera, it immediately flipped entirely over to show it's orange underside.
I'd not seen that behavior before. The few I've found in the past would just show the bright red tail curled up.
I guess that these are defensive/distraction behaviors, though I have trouble understanding how making part of yourself look more like a fat juicy worm would be at all helpful in most cases.

I tried getting one more photo as it quickly took off, but I wasn't fast enough to get a good shot.

Friend sent photos of a ”sluggish,” 3ft long, slender snake they encountered while hiking at Henry W. Coe State Park today for I.D. Photo credit: A. Skinlo.

Pacific Gopher Snake (Pituophis catenifer ssp. catenifer) A poisonous snake can hurt you if you eat it.
A venomous snake can hurt you if it bites you. This snake species is totally harmless.
"Adults range in size from 3–7 feet. They are "active in the daytime, and at night in hot weather. They are one of the most commonly seen snakes on roads and trails, especially in the spring when males are actively seeking a mate, and in the fall when hatchlings emerge. They are a good burrower, climber, and swimmer.
When threatened, a gopher snake will do several things, sometimes one after the other, including: crawling away quickly to escape or hide; freezing up - making the body rigid and kinked up so it won't be noticed or perceived as a snake; and striking at the threat to scare it off. Gophersnakes also use a more dramatic defensive behavior - sometimes a snake will elevate its body and inflate it with air while flattening its head into a triangular shape, hissing loudly, and quickly shaking its tail back and forth to make a buzzing sound."

A Guide to the Amphibians and Reptiles of California
https://californiaherps.com/snakes/pages/p.c.catenifer.html

Pacific Gophersnake - Pituophis catenifer catenifer (range maps and more)
http://www.californiaherps.com/snakes/pages/p.c.catenifer.html

Key to California Gophersnake Subspecies http://www.californiaherps.com/identification/snakesid/gophersnakessubspecies.html

Colubrid Snakes (Family Colubridae) Most colubrids are non-venomous, or have venom that is not known to be harmful to humans, and are mostly harmless. Some colubrids are described as opisthoglyphous "rear-fanged," meaning they have elongated, backward-facing grooved teeth in the back of their upper jaws.

The Reptile Database: https://reptile-database.reptarium.cz/species?genus=Pituophis&species=catenifer&search_param=%28%28search%3D%27pacific+gopher+snake%27%29%29

Description, info about Pacific Gopher Snake (Pituophis catenifer ssp. catenifer)
https://www.inaturalist.org/taxa/51440-Pituophis-catenifer-catenifer

https://a-z-animals.com/blog/gopher-snake-vs-rattlesnake/