My device is almost unusable, how do I know what's slowing it down and breaking it?

[MirceaKitsune]

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?

[RichH]

Go into recovery mode (vol up + Home + Power key) and clear cache. This will clean out bits of programmes that are left behind from installing/uninstalling apps. If that doesn't work you will have to go for a factory reset (also from recovery menu).

[stonkr]

I'd also recommend restarting the phone every day if you don't switch it off to charge it.

My S would gradually slow down over time unless I cleared the cache and dalvik cache (root only) every few weeks and restarted at least once a day. But then I did/do have just over 200 apps installed.

[Goots]

I turn my SGS off every night now, it's just a habit I got into and it stuck.

Before I had a smartphone, I never used to turn my mobile off, ever.

I think smartphones need to be rebooted every now and then, it is a miniPC after all

[MirceaKitsune]

I entered the recovery console and cleared the cache. I also discovered and installed custom launchers, which are faster than the official TWlauncher (can't believe how much time I spent with that one, which is very limited in comparison). So far it seems a little faster and more stable, but not a lot.

[MirceaKitsune]

Well my phone still restarted on its own yesterday... even if apparently it doesn't jam any more. Anyone know what can cause it to restart without a shutdown command?