Early signs of autism

I know You can’t really get diagnosed until around 4-5 but for children who have been diagnosed what are some early signs looking back? My daughter is 15 months and her father has two other children that are autistic. I’ve googled somethings but she’s still very young. Example. She doesn’t really respond to her name but if I say look or here she will make eye contact with me. She spins her toys, she does not like being held, when she cries the only way I can calm her down is singing (saying it’s okay, what’s wrong etc etc doesn’t work she cries harder) she doesn’t like being held at all. She screams. Like random screaming all day. She also hits her head against things in 3s she isn’t upset when she does it she just randomly does it sometimes. I’ve noticed hand flapping but she’s still young and think maybe her just being that age but she does flick her fingers. Also when she eats she picks it up drops it and then picks it back up.