My cat vomits right after eating and goes to the litter box around it, worse at night; what is wrong?

A cat vomiting hairballs, if frequent, suggests hairball syndrome or gastroenteritis. When the cat’s energy is good, fast and withhold water for a day, use an antiemetic, and give probiotics to regulate the gut.

After vomiting stops, give hairball paste or cat grass, which both supplements nutrition and helps pass the hairball. If no improvement, see a vet. Usually brush the cat often to remove loose fur and occasionally give cat grass to prevent hairballs.