My Imac display starts flicker after macos sequoia 15.0.1 please suggest any solution 
Hi bro, the device is under warranty correct?
Try to Press and hold power button on the back of iMac for 20 seconds and it will restart. check if the same problem continues. We need to check with nearest apple authorised service center if the issue didn’t fix bro.
This could be hardware related issue triggered after software update possibly.