It sounds EXACTLY like the night terrors my daughter went through. She didn't have them with naps, but I don't think that makes a difference. My daughter's happened within 2 hours of going to sleep and they lasted between 15 and 45 minutes. The more we tried to console her the longer they lasted. We had an amazing pediatrician who has been in practice for about 45 years. He assured us that night terrors have NOTHING to do with the child's level of happiness. He said they have nothing to do with nightmares and it was nothing we did wrong as parents. We did notice they were worse if she was overly tired when she went to bed. The hardest thing in the world when your child is crying like that is to not touch them, but we eventually learned if we just put her on the floor (so she didn't fall off the bed) and sat near, but we were quiet and didn't touch her, they would stop much faster than if we tried to hold and talk to her. It was harder on us than her. She never remembered the episodes at all. This is from a night terror website:
"Nightmares occur during the dream phase of sleep known as REM sleep. Night terrors occur during a phase of deep non-REM sleep usually within an hour after the subject goes to bed. This is also known as stage 4. During a night terror, which may last anywhere from five to twenty minutes, the person is still asleep, although the sleepers eyes may be open. When the subject does wake up, they usually have no recollection of the episode other than a sense of fear."