I definitely know what you mean about leg muscle issues on Seroquel. I've been prescribed it on and off throughout the years for insomnia and BPD. The leg cramps happen to me, too, especially with higher doses - it feels almost like restless legs or opiate withdrawal. Never bothered me too much, though, because even if I'd be kicking my legs a bit I'd still be knocked out after a couple minutes of lying down.
BTW, 25-50mg is totally fine to be prescribed for insomnia. That's an extremely low dose, as I've heard of some people with BPD/schizophrenia being prescribed 800+mg a day!
A few tricks that might work to aid leg muscle pain/cramps:
-Exercise/stretch your leg muscles daily
-Stay hydrated by drinking plenty of water
-Some herbal relaxants such as chamomile tea, valerian root, or kava can help
-Take an anti-inflammatory with the seroquel (such as naproxen, ibuprofen, etc.)
-Take Magnesium supplements (you can find these in pharmacies or vitamin stores)
-Take Potassium supplements (also found in pharmacies/vitamin stores)
-Eat foods high in magnesium:
See which foods here.
-Eat foods high in potassium:
See which foods here.
Remember, these methods may or may not work for you - they've worked for me, and others have vouched for them as well; however, it is important to make sure with your doctor that they are okay (especially with the herbal supplements).