From the model number, it sounds like a lower end fully automatic Denon direct drive turntable. A lot of Denon direct drive turntables have a magnetic strip on the inside of the edge of the platter. A device that looks like a head from a tape recorder is usually mounted on the surface of the turntable under the platter.
If the "tape head" type thing came loose you will need to carefully put it back where it was mounted. There are usually marks where it was positioned if it did move. If the magnetic strip with the encoding information is damaged then you have a paper weight there. It is pretty much impossible to find a replacement platter unless you get very lucky.
The other possible explanation is that the turntable is getting old and the electrolytic capacitors are drying out and causing a failure in the servo control circuitry. If the capacitors are shot you can try replacing them (or having them replaced) but other items in the curcuit could have been damaged if the capacitors are shot.
I own a Denon DP-62L and it has a proprietary microprocessor/speed controller integrated circuit that is another point of failure that you don't want to cross. There are no replacements for a Denon speed controller IC, if your turntable has something similiar.
The good news is that other than the platter, pickup head and speed controller, all of the other electronic parts are pretty much garden variety OP amps and transistors. If it is worth it to you, you could get the turntable fixed but a replacement could be a more economical route.
Start by checking the platter and pickup head to make sure they look undamaged and looks like nothing has gone wrong. If those items look OK then don't power the table on again. The malfunction can cause further part damage in the turntable electronics. The potential exists that a speed controller IC may be damaged if your table has one in its circuit.
If you have a local repair shop try taking the turntable there and see if they can give you an idea of what you are dealing with.