The word "himself" focuses on Jesus and the surprise of Jesus actually appearing to them. Most of them had not seen him after his resurrection. (See: [[rc://en/ta/man/translate/figs-rpronouns]])
"startled and afraid." These two phrases mean about the same thing, and are used together to emphasize their fear. (See: [[rc://en/ta/man/translate/figs-doublet]])
# supposed that they saw a spirit
"thought that they were seeing a ghost." They did not yet truly understand that Jesus was really alive.