My child has recently started to wake up terrified, with glassy eyes and crying. Is he having nightmares? After some time, he just goes back to sleep.

same goes to my little one, its been quite sometime now, she keeps on crying at night and seems like having a bad nightmare. Upon my observation, she'll cry at night whenever I am asking her not to do this etc. So we are trying as much as we can not to shout or scold her but still letting her know that is bad in calm and nice way.