Salam,
Bismillah.
Bismillah.
Narrated Abu Huraira:
The Prophet said, "Isn't he who raises his head before the Imam afraid that Allah may transform his head into that of a donkey or his figure (face) into that of a donkey?"
Isn't he afraid? There was a man we get to know about, who challenged this Hadith. He raised his head before the Imaam intentionally during prayer, and Allah turned his face into that of a donkey (or somewhat similar to it). Later on, he repented. [Can't find a historic reference for this incidence. Let me know if you can help with it. Jzk.]
Anyway, the lesson here is: 'follow' your Imaam. Wait for him to make his move, and then repeat after him. During Salah, wait for the Imaam to say his takbeer, change his position, and then change yours. 'Kay? :)
Wassalam.