Your pet could have eaten something that tasted bad.
There could be a problem with the teeth or dental pain. An example would be an abscessed tooth.
When pets are nauseous then may drool.
This is pretty rare but when a pet has the rabies virus, the nerves that allow them to swallow become paralyzed. If your baby is current on the rabies vaccine this should not be a problem.
Neurologic disorders that affect their ability to swallow can cause hypersalivation.
Kidney disease can cause mouth ulcers which can cause hypersalivation.
Sometimes younger pets bite electrical cords, causing mouth burns which can cause hypersalivation.
If they have a foreign body stuck in their mouth, or the back or the throat, they may drool.
There are drugs and toxins that cause hypersalivation. Some examples are caffeine, insecticides containing boric acid, illicit drugs, animal venom (black widow spiders and scorpions), Toad and newt secretions, Certain plant consumption, and household cleaning product consumption.
I would start by flushing the mouth with water in case your pet has a bad taste in the mouth. Then get a flashlight and take a good look around the mouth. Check to see if there is anything stuck or if you see any redness or drainage around the teeth. Look for ulcers or signs of trauma.
Then you can offer a little milk, and a piece of bread, in case there is a bad taste in the mouth.
If your pet continues to hypersalivate, they will become dehydrated so I recommend you seek veterinary attention.
If your pet may have been exposed to a toxic substance seek veterinary care at once.