Aw, yan talaga ang normal baby behavior, momsh! Sa 7 months, ganyan talaga sila kapag excited or interested sa something new, yung shaking at stiffening ay parte lang ng kanilang way of processing and expressing emotions, kaya don't worry. A few of us mums noticed the same thing sa aming babies around that age, especially when they see bright colors or new toys, parang mini fireworks lang ang body nila pag happy! Just keep an eye na walang fever or unusual behavior alongside it, but honestly, kung kaya siyang mag-play normally at kumain nang maayos, it's mostly just excitement. If you feel uneasy talaga, you can always check with your pedia just para ma-ease your mind, pero based sa dami naming napanood, it's really just that developmental stage!