Perhaps increasing your calcium and potassium intake might help?! I use to experience really intense calf cramps that would wake me up at night... they were absolutely excruciating! I now eat a banana, pretty much daily as well as taking calcium and potassium tablets and have found it really helpful. I also take a high dose of vitamin D which might have contributed to my relief too.
Anyway, just a thought!
Yes antipsychotics can commonly cause temporary movement disorders such as akathesia (motor restlessness) and dystonia (stiffness). All of this can be treated with a side effect pill. Speak to your psychiatrist about this.
Yes muscle tremors are a side effect yes and a common one but not painful ones - have you spoken to your doctor? There are things that can be done and perhaps a dosage adjustment might prevent or minimise, I get them myself along with cogwheel rigidity and tremors but I have no pain from mine.
If you google Seroquel XR side effects you can find the information leaflet on the drug