Name is Greg and i will assist you the best i can, please Only accept if you are happy with my answer.
When the Hold light comes on or blinks then this is telling you the transmission management system has encountered a malfunction with in the system when it does it will switch on the hold light.and store a code in the TCM Transmission Control Module.(Management control system ).
What you have to do is visit your local Dealer or Garage that has the equipment to scan for codes to see what problem you may have. from the codes the testing technician will know what has to be rectified to stop this happening again.
When you switch off the engine then switch it back on this will clear the code and switch off the hold light , the hold light will come back on when the management system encounters a malfunction again
Need further assistance with this issue please get back to me.
Kind regards Greg