I want to turn on NRF 51822-S110 radiO

[meria]

I successfully turned off bluetooth radio using NRF_RADIO->TASKS_DISABLE = 1 when i do advertise_start(); after certain delay i coudnt connect back for data transfer

[Petter Myhre]

When the SoftDevice is enabled some peripherals are blocked/restricted. See Section 11.3 in the S110 SoftDevice spec. The radio is blocked, so trying to access this will cause a hard fault. If you are not connected to anything and you are not doing advertising the radio will not be used, you don't need to "turn it off".

[Petter Myhre]

It is difficult to solve "this" with the very limited information you have provided. I suggest you first read this. Then you create a new question with more information. Like what the actual current consumption is, more details of what you are doing in your application, and how.