I was reading Qur'an at a time then I stopped. Now after some months, I want to start reading again but I want to start from the beginning. Can I start from the beginning again or should I continue from where I stopped?
There is no restriction or fix rule, you could start at the verse you stopped from to complete a recitation (khatmah) -which is a recommended act according to sunnah- or restart from the fatiha.
On the other hand it is not recommended to start two or more parallel khatmah!
And keep in mind:
Narrated Muhammad bin Ka'b Al-Qurazi: "I heard 'Abdullah bin Mas'ud saying: 'The Messenger of Allah (ﷺ) said: "[Whoever recites a letter] from Allah's Book, then he receives the reward from it, and the reward of ten the like of it. I do not say that Alif Lam Mim is a letter, but Alif is a letter, Lam is a letter and Mim is a letter." (Jami' at-Tirmidhi)
This is the statement of this fatwa.
And Allah knows best!