Sounds as if the microUSB connector in the phone is wet. Take the battery out of the phone. Blow on the connector gently to get any saliva out of it, then dunk the phone into rubbing alcohol (the kind you get at the drug store) until the entire connector is submerged and swish it around to get all the water and chemicals out of the connector. (Alcohol isn't water - it's hygroscopic and absorbs water.) let the phone dry overnight, then put the battery back in and see if it works.
Saliva is acidic and it's full of germs that attack things like plastic and metal. If nothing's been damaged too badly yet, the alcohol will clean everything up and the phone will work. If not, you'll probably have to replace the motherboard and, unless the phone is insured against water damage, or it's a high-end phone, it probably won't pay.
(Putting the phone into uncooked rice won't help - the water will be absorbed, but the corrosion will continue and eventually the phone will stop working.)
