Dependent origin operating mind During  walking meditation it happens automatically,without any initiation.understanding of dependent  origin lead to fear of sansara. Is it the doer of the  mind cause upadana?
During walking meditation it happens automatically,without any initiation

There is an intention (Cetana) behind every movement in the walking meditation. If you look carefully it can be seen. There's e.g. an intention to lift the foot, move it, lower it, place it, etc. With practice one will begin to see intentions everywhere such as the intention to swallow, to blink, even behind a thought, there's an intention to think.
With consistent practice this part of reality will reveal itself.