Dreading Naptime

My son is two, and I live in absolute dread of naptime. It's not the getting him to sleep part, it's the waking up. He almost always wakes up in a horribly foul mood. He whines and cries about everything and just generally does not know what he wants. It turns into an hour or so long ordeal every day. While he was still breastfeeding, he would nurse until he settled down, but now that he has weaned there doesn't seem to be anything to calm him down. I am at my wits end. I don't know if it's allergies, teething, night terrors, or just plain grumpy tantrums?? Has anyone else gone through this? I'll also add, my oldest did this on occasion and was not breastfed.