ref: https://btc.com/

i am watching how often new blocks gets generated.,

imho i read somewhere , it stated new block gets generated every 8-10 minutes.

but sometimes it takes 30 minutes for new block to appear and sometimes more than 1 block gets generated in 5 minutes.,

why is that ?

who is controlling it ?

isnt there enough hash power already to generate blocks. ?

what am i missing here ?