Hello @v-yetonggu-msft ,
Thank you for your suggestions, I'm getting a lot closer to the solution 🙂 I implemented your suggestion but it failed on the first try again:

I then found another useful topic to try changing the POST to PATCH. I think PATCH is more accurate for my situation since the _ModerationStatus before running the workflow on this item is Pending (2). When I tried it with PATCH I got the following error:

Appreciate your thoughts!
Update:
I added the header:
If-Match: * and that fixed the eTag error. Now the error is:

A type named 'SP.Data.IMS_x0020_Working_x0020_AreaListItem' could not be resolved by the model. When a model is available, each type name must resolve to a valid type.
The IMS Working Area is a Document Library. Might this be the problem?