My baby shakes his head like saying no, a lot. is that bad

Hi. My baby (7 months) recently started shaking his head as if saying no. At first I thought it was the cuttest thing !! But my mom (Mexican) says back In her day. That was bad. Why? That it meant baby maybe Had meningitis. !?! do I have nothing to worry about?? He doesn’t cry when he does it sometimes he’s smiling while doing it others just calmly while he’s watching his toons (cartoons) I’m a first time mom so I apologize for the question being “dumb” thank you!