CD-ROM will not start spinning

My CD-R/RW Ricoh 7040A worked OK untill – it sometimes does not start spinnin/rotating after a CD is inserted; I opened the case and if not it does not start rotating give the CD a small push in the rotating direction, and from now it works OK, untill a new CD is inserted. Any tips/hints, what the problem might be? The PowerSupply is a 300W, only two other HD+FD are connected. OS=WIN NT4.0 WS. Already tried changing cables.