why did my engine loose lots of oil right after an oil and filter change and starting up the car?

What is your question?

After the last two oil changes, I started the car, and then oil spewed out somewhere behind the oil pan. When I stopped the engine, the oil stopped running out and is ok now. Why?

What makes this problem better or worse?

simply changing oil.

How long has your 2018 Toyota Camry had this problem?

Once 5000 miles ago at oil change time. Again the last week - same scenario.