My phone is hardly 2 week old at the time of posting this question , I went through the answer provided on this site regarding screen flutter on Moto g62 5g and cleared all the cache but it didn't go .
I switched off the bedtime mode at that time and it didn't flutter at all but after 7 days while fastly scrolling through YouTube video comments the lower part of the screen started fluttering again as of your question the flutter occurs momentarily for 5 seconds and the colour reverts to normal in both bedtime off and on modes
Sorry for the late reply as I didn't observe the flutter at all after switching off the bedtime mode so I thought it must be a glitch or something like that
I made you the owner of the original guest post to make it easier for you to find.
I'm guessing a hardware issue, but it's hard to tell, because it sounds like it doesn't happen very often (so it'd be difficult to narrow it down using Safe Mode).
Is the phone still under warranty? If so, contact Lenovo/Motorola.