I am afraid I am not familiar with the Samsung model in particular so I will give you a few general tips that may get you going.
1- Make sure you hear the spindle motor spinning the disk to an even speed.
If it seems to be speeding up and slowing down you could have a dirty/bad optical pick up assembly.
2-Try with different DVD/ CD to isolate.
Many times it is just the disk is dirty scratched and the player cannot reliably read information from disk.
3-Look for signs of lubricant/dirt on/under the player tray or on disk.
I have had optical drive mechanisms spit lubricant and have left an oily film on the pick up unit causing this.
4-Clean the pick up unit.
Be very careful with this one as some units are mounted on very flimsy suspension/posi
5-Re-seat all the connections inside.
A loose SATA or Data cable may be all that is stopping the information from the disk from getting to the circuit board.
6-Swap the drive with a known good one.
Many set-top DVD players use Laptop or PC sized drives with the same connections. I have fixed a couple of Sony set-top players with drives from broken Sony laptops.
Hope this at least guides you to a possible solution.