Does this sound like autism ? 18 months old

I am extremely worried after just watching a video of a woman giving her warning signs of her baby having autism and I noticed that my daughter does almost all of them?

- started saying words around 8-10 months old like dada , then she would say hi alll the time like hundreds of times a day, sit (telling the dogs to sit ) mama & then out of no where I have realized she doesn’t really say any of it any more. Randomly I will hear her say hi once or sometimes a random mama or dada every few days.

But it’s mostly babbling sentences now.

She flaps her arms a lot. She walks backwards a lot.

Could this just be normal toddler behavior or is this not normal?