Not reading disks

Your spindle motor has gone, this is not impossible to solder another one in, and should be considered as these Sega consoles are getting rare over time. You will notice that it will attempt to read the disc but will just stop after 3 seconds, failing that open the machine and put a bit of tape at the back of the GD drive where a little lever is to keep it down as the lid maybe out of alignment.

its a very old console that is probably it and you should just accept its life is coming to an end. Sorry, it is a classic item.