I did something similar during one of my withdrawal stints. Granted, I had already been prescribed seroquel/quetiapine for a couple of years and was still taking it sporadically, but either way I took it and pretty much slept through the worst few days. I don't have to reiterate what others have already told you but I will anyway: you won't run into any problems in terms of withdrawal. I took 50-100mg of seroquel nightly for a solid few months and basically stopped without any real issue... to be honest I very rarely hear seroquel referred to as a drug of concern re: physical dependence and withdrawal.
Just out of curiosity, how much are you taking? You don't say, so I don't want to go on a whole thing if you already know but keep in mind seroquel can be effective for this kind of thing at really small doses, 25-50mg.
Keep up the good fight! If the seroquel helps you could very well sleep for the better part of three days like I did. I mean, it wasn't good sleep nor was I coming off a giant dose at the time, and when I woke up I was miserable. But seroquel + thomas recipe foods/otc meds minus the benzo really was a godsend at the time. I think I actually took the seroquel for 3-4 days and spot checked the anxiety or trouble sleeping with small amounts of alprazolam for a few more days but I'm not necessarily recommending a benzo for someone just coming off opiates. That's just what I did at the time.
It didn't stick, but was the start of my longest stretch without so... do with that what you will.
TLDR: As others have said you'll be fine. I did something similar and it helped. Good luck with your recovery.