We had this a lot with Olivia, and truth be told,we still do, even though she is able to articulate well. She is at the point where she can understand that she is frustrated, but still doesn't know why.

SO I have no solutions really, just that talking and helping them vent means that you can nip the kicking in the bud.

The only thing that helps with Olivia and her red headed angry tanties is "When you feel this frustrated and angry darling, take big big deep breaths" (We practice together for a few minutes and it usually is enough distraction to diffuse the situation........