He doesn’t know how to express his feelings and that’s the only way he knows how. You just have to sit with him and let him feel his feelings until he stops or as the comment above says try and distract him. You won’t be able to ‘get a handle on his tantrums’ until he’s about 5 unfortunately.
Please don’t take that he only acts out with you, I see it as it’s your there safe space to share they’re emotions with, they know you’ll take care of them and help them feel better x
My son is 17 months and started head banging etc at around 15 months. I literally just ignore the behaviour and try and distract him - I usually look out the window and say “look at the birds” or something like that (he’s bird mad 🤣) you’re not failing him! It’s a completely normal behaviour, it’s such a difficult age where they’re trying to communicate but can’t verbalise things so they resort to head banging. Distraction has really worked for me! Xx