I had this problem to the extreme and stopped Seroquel.

Now I am back on it, with Atarax (or to a lesser extenet Gabapentin) to ameliorate knee jerks. As a result, I sleep well. Seroquel is the best sleep med for me. For mood, also is very good, though I am somewhat hypomanic and the pdoc and I are watching. I am enjoying it, but one has to be careful, as we all know.

Atarax 100 mg works for me with 600 mg Seroquel. I would imagine that 50 mg Atarax would be enough for you on 100 mg Seroquel. Maybe even start with 2 mg. Atarax is a sedative antihistamine.