1.5 year old daughter... should i be concerned?

My almost 18 month old is definitely showing signs of terrible twos. The only thing that worries me is she is hitting herself and me when throwing tantrums. She also throws her head forward and back to hit things such as the couch or her crib railing... is this normal? She seems to take her anger out on herself?! She's my first so im not sure if this is normal.