my 4 months daughter continuously makes hmmmm sound and grinds her lower lips, pl. suggest

A. As babies begin teething, they may begin to grind their teeth while awake, asleep or both. Teeth grinding — called bruxism — is a fairly common issue. According to medical experts, 20 to 30 percent of children grind their teeth or clench their jaw, often during sleep or as a reaction to stress.