do not disturb keeps turning itself off overnight

sadly it seems the only option but I will not be pleased if I go through all that and it doesn't fix

Just make sure you do a full backup with both Samsung and Google and at least you can do a restore it if needed.
 
Did you end up doing a factory reset?

I'm having the exact same problems, but I have a S10e. Imported everything from an old phone, wondering if that's what my problem is too. I had a DND schedule setup, but accidentally set it too early. Didn't realize that's what I had done for a few weeks, thought it was just the phone shutting the DND off. Changed the DND to end at 11am, so that I could turn it off when I wanted too. It still turns itself off about 6am (which is NOT when I had accidentally set the end time for, I just happen to be up this morning and watched it happen). Getting really tired of being woke up by spam email/calls/texts!! Anyone have a fix for this yet??? Thanks!!!!
 
I am having the same problem! It just started happening in the last week or so. I’ve turned the DND off and on, reset it, etc. my phone auto restarts only once a week but this is happening every morning. I have no idea what time it’s turning off (I have it set for 7) but when I get up at 6 it’s already off. It’s not a Sprint thing..I’m a Verizon customer.
 
I am having the same problem! It just started happening in the last week or so. I’ve turned the DND off and on, reset it, etc. my phone auto restarts only once a week but this is happening every morning. I have no idea what time it’s turning off (I have it set for 7) but when I get up at 6 it’s already off. It’s not a Sprint thing..I’m a Verizon customer.

I'm having same issue Android 9, Sony xperia