Baby shaking head from side to side

My 5 month old started shaking her head side to side like she is saying no.. she does it when she is lying down or standing up with a support... she shakes for a few seconds and then looks at us... does that a few times... I googled it and as usual it was a big mistake ( things like autism popped up)... anyone else whose LO does this or has done it???

I know she was trying to dance when she was doing it standing up as we were singing and she was trying to copy my mom who was doing the same thing....