Hi Darshana,
On the EOS 5D Mark IV the Multiple Exposure function is only available in P, Tv, Av, or M modes. That function will stop working if the camera is put into Auto, C1, C2, or C3.
If you would like to view information on using the Multiple Exposure function it is on pages 268-275 of the manual. If you need a copy of the current manual it is available HERE. Once you are on the web page click on the Manuals button and the one to reference is named EOS 5D Mark IV (WG) Instruction Manual.
