I'm on clonazepam with Seroquel as well, plus Gabapentin and Lamictal. (Lithium is pending when I see my pdoc again).
The clonazepam definitely helps ease me into the effects of the Seroquel, if that makes sense, where a little sedation starts before the Seroquel really kicks in. The clonazepam definitely helps me relax at night. I used to take it PRN, but due to recent stressors and bad episode, I take it 1x per day, sometimes 2x, but I try not to, since my pdoc does not want me to take it too much.