Several medical conditions and medications can cause difficulty sleeping - some of these include pain related conditions, neurological conditions, cardiac conditions and kidney disorders such as kidney failure and medications include medications used to suppress immunity some of which are given after kidney transplant, medications used for hypertension etc. In your case it is possible that status of your transplant/overall functional status as well as the medications that you are on may be causing some the sleep disturbances. Please see your physician for further assessment and possibly treatment.