Won't start...99 cadillac deville...no juice to the starter

My 99 deville wont start sometime unless i rock the car back and forth a few times. while its moving alittle i can start it. i tighten my battery cables. also my have a gasket leak. can that affect my starter too?

Hi, can you hear a clicking noise when you turn the key to start as the starter gets its power direct from the battery so also check these wires are connected and not came loose.
If you can hear a clicking noise when you turn the key this means the starter motor needs replacing ok.
Let me know how you get on or if you need further assistance ok