When you first begin ssri's, do you experience sleep disturbances and psychomotor agitation?

Sometimes: It can be a side effect an a reason to move on to another medication. You should call the doctor and discuss the problem. Most people do not experience that problem.

SSRIs and sleep: Sometimes people will experience an increase in insomnia but that should go away. But if you have increased insomnia for more than a couple of weeks talk to your prescribing doctor. If agitation is significant let your doctor know right away--they may decide to have you try a different med. But strongly encourage you to talk to your doc and not just abruptly stop meds.