Wild caught baby Garter won't eat...

[RedSidedSPR]

Stay away from: Goldfish, Rosy Red Minnows, Red Wrigglers, Crickets and anything wild caught except worms and slugs.

[aSnakeLovinBabe]

the shape is all wrong to be a northwestern, northwesterns don't have big heads.

[RedSidedSPR]

It's a baby... Bit I still don't think it looks northwestern

[kibakiba]

That is true. I had a hard time figuring out the pictures, but I had just gotten up when I saw the pictures.

[Azurascender]

Looks like a checkered to me, Thamnophis Marcianus. But the dots on this one look a little less symmetrical, and the yellow spine is less profound.

[RedSidedSPR]

I don't think it's a checkered, but it does look like one

[guidofatherof5]

Without the closeup photos I saw Checkered.
Checking the range map took them out of the running and the chances that you caught a wild Checkered baby on the beach in your area is very unlikely.
I think Shannon is correct with her ID.
Wandering Garter Snake(T. elegans vagrans)
If it turns out to be something else then I change my mind to that
Snakes - Living with Wildlife | Washington Department of Fish & Wildlife

[RedSidedSPR]

The mark of an expert

[brain]

looks like t. elegans vagrans to me! Wandering Garter Snake.

T. elegans vagrans here on Whidbey are more a choclate brown with flicks of orange or an orange stipe. Interesting

I would have said checkered

[drache]

welcome to the forum
some Thamnophis e.vagrans (wandering garter) can look very similar to some T. marcianus (checkered garter)