Recently, my 19-month-old daughter has been having a "new" kind of tantrum. Before, she'd have tantrums (some yelling, crying, lying on the floor) when frustrated (e.g., if told no or had something taken away). These make sense to me as typical toddler behavior.
However, in the past week she's begun a different behavior. She will seemingly out of the blue just start crying, screaming, and writhing on the floor. Nothing identifiable sets this off. She's inconsolable during this time, and doesn't respond to questions she will ordinarily answer (e.g., does your tummy hurt? do you want something to eat? want mommy to hold you?). She will ask to be held then fight to be put down. Nothing soothes her. These episodes can last about 10 minutes, and then she'll just recover and be back to normal. In between, she's playful, funny, energetic, and her typical self. Her development has been absolutely normal thus far. She's smart, verbal, playful, social, and generally good, though I would describe her as having a strong personality.
No fever or other signs of illness, though she did just get over the stomach flu a week ago. There has been a bit of upheaval in the family lately -- we've moved twice in 6 months, both parents are a bit stressed. She's been having some trouble sleeping (night and day), so is certainly tired and we're working hard to resolve that.
Is this normal behavior? A sign of psychological distress? Physical illness? Should we worry? Our own pediatrician didn't have any idea what to think.