I realize something drastic must be done, and I start all over at the beginning.
【答】over 一词，其中一个意思就是again 之意。之前加all 表示强调程度。
所以，start all over 没错。
修饰关系是：all 修饰over；all over 修饰start。
start over：PHRASAL VERB If you start over or start something over, you begin something again from the beginning. 重新开始 [美国英语]
例：
...moving the kids to some other schools, closing them down and starting over with a new staff.
…把孩子们转到其他一些学校，关掉它们，然后招一个新员工重新开始。
It's just not enough money to start life over.
这些钱根本不够用来开始全新的生活。