Tantrums after sleeping

Lately, my 15 month old son has been waking up from naps and bedtime in the worst mood. He screams at the top of his lungs without end. My husband and I try to calm him with the usual. Change diaper, check for anything that could be hurting him, offer drink and snack, toy distraction, snuggles, talking calmly to him. Nothing works. Nothing helps. He is not still tired because he sleeps really well (2 hr midday nap and 10-12 straight hours at night).

There are no tears during the tantrums.

They will last for around an hour.

Usually he is a very mellow and happy baby.

I love my son and dont want him to grow up too fast but I live for the day when he can tell me what's wrong.

Any advice?

Is this just another unpleasant toddler phase?

My husband and I are struggling.