Hello I understand your concern At 4 months, increased salivation and mild irritability are very common and often a normal part of development — especially as babies start to explore the world more with their mouths.

Mouthing is normal part of development in babies seen during 4-6 months ..Along with salivation . But consult pediatrican if he has other symptoms like cough ,cold ,hurried breathing ,excessive crying

It's normal

Excessive salivation and drooling is normal for the age as the baby develops increased coordination of swallowing. Do check for gum swelling - it’s a little early for teething but some children do develop the symptoms earlier and will like to mouth on objects at the time. It’s ok to give paracetamol occasionally to relieve pain - if it’s giving relief to the baby Do be careful for any other causes of crying - fever, stomach issues, temperature discomfort, over wrapping