Hi Sherrill. Let me start of with suggesting to reset you iPod.
1. Toggle the Hold switch on and off. (Slide it to Hold, then turn it off again.)
2. Press and hold the Menu and Center (Select) buttons simultaneously until the Apple logo appears, about 6 to 8 seconds. You may need to repeat this step.
Tip: If you are having difficulty resetting your iPod, set it on a flat surface. Make sure the finger pressing the Select button is not touching any part of the click wheel. Also make sure that you are pressing the Menu button toward the outside of the click wheel, and not near the center.
If the above steps did not work, try connecting iPod to a power adapter and plug the power adapter into an electrical outlet, or connect iPod to your computer. Make sure the computer is turned on and isn't set to go to sleep. Try resetting the iPod while it is connected to power.
If that does not work try to restore it ( you will lose your music)
http://support.apple.com/kb/TS1441 here are the instructions for that.
Should this still not work I believe that you you have a Hard Drive error. Since it is a 4th Generation, I would try to format the HDD. This is where it might get a little tricky. Plug in Ipod and when windows recognizes it, right click on the ipod in My Computer then select format. You will get several options first try selecting quick format. then exit and restart itunes. Itunes will say it needs to reset factory settings. Do this and follow prompts. This does not always work. Sometimes you have to do a full format inside My Computer which simply means that I did not tick the quick format box. Then repeat the itunes process. If this still does not work after all that, do another quick format in My Computer. Please do remember that for this ipod to finish restoring you will be asked to unpug it from your computer and plug it into a wall charger. That is the final step for the restore. So make sure you have one available. I hope this is not to confusing. http://support.apple.com/kb/TS1441 and http://www.methodshop.com/gadgets/ipodsu... and have more info. I do hope this helps....good luck