How can i fix my 1996 VW transporter 1.9tdi 888 special?

I have a 1996 VW Transporter 1.9tdi 888 special. The problem is when i go to start her up she will not bite. That then drains the battery... I have since charged the battery but when i try to start, there is nothing, just a click & a slight turn... I did get a tow to jumpstart her & she went on the first try, i drove her for a while & let her idle outside my house. I turned the engine off later & left her for about an hour... she started with no problems first time...Great, i thought, until the next morning when i went to start her & there was nothing AGAIN!!!
Any help would be very very much appreciated.... Thankyou in advance for your time & knowledge.