I've been wanting to post this for a long time. I've installed several applications on my Galaxy S over the time, though few of them run in the background (or should). Still, my device has become almost unusable. It barely works (extremely slow at times), gets stuck very often, throws me out of menus, and every few days it shuts down on its own and restarts (it plays the shutdown song and logo). I often have to remove the battery to get it working again, and once had to wait more than 10 minutes to fix it and make a phone call. When not used, the battery lasts less than 2 days (with background data, wifi and bluetooth disabled).
How do I find out what's causing this, and make my device work acceptably again?