R.O.D,
There are a couple of basic troubleshooting steps you can take that may help.
Firstly you can format the player incase there are any problems bad sectors or corrupt files. If there are any files on the player you want to keep copy them back to your PC before you format.
Secondly you can extract the firmware from your player using s1fwx, repair it by running the repair.bat in the s1fwx folder then loading it back to your player.
You can download s1fwx
HERE and there is a guide to using it
HERE
Just so there will be no suprises when you format your player there are players on the market that are sold with hacked memory chips that read as being larger than they really are. Player restarts are a common symptom of this. If your player has a hacked memory chip when you format it the hack can be removed and the true size of your chip will be revealed. This may not apply to your player but you should know about the possibility. You will find other posts about this problem in the forums, they generally have titles about Memory problems.