If you are capable, open your PS4, the disc drive is easy to get at, so remove it completely so that you don't damage any cables. You will find many videos online showing how to do that or use intuition. You have to be aware at all times of ribbon cables and the laser lens, these are fragile .The rollers that take the disc that closes the drive or opens it depending on whether a disc is present - this mechanism can be removed with care. One spring and 2 holes either side securing the disc block, be careful not to apply too much pressure here. Once this is out use some rubber rejuvenater or white spirits to clean the rollers and give them some grip. Flip the drive and manually move the motor that operates this mechanism to test any problems with the cogs. While you have gone to the trouble to get here why not clean all dust from the drive. Reassemble and test your PS4.