afraid of the dark nightmares

So I know this is weird and probably not possible but does anyone know if it's possible for a 5-6 month old to a) be afraid of the dark and b) have nightmares?? My son wakes up screaming but can easily be comforted back to sleep as of he wasn't really awake other times he wakes up really screamed like something scared him. We know his scared cry because he has gotten scared before. He's also starting to weep in his sleep during naps resulting in waking up screaming.... and if he wakes up in the dark or is in the car and it's dark he's screaming ....