This should work to clear the cache partition. But read below before trying this. I'm not at all convinced your problem is caches.
To clear the cache partition:
1. Launch the Settings Application
2. Tap on the General Tab(if in tabbed view)
3. Scroll Down and Tap on the ‘Storage’ Option
4. Locate the ‘Cached Data’ Option and Tap on it
5. Confirm the Task by Tapping on the ‘OK’ Option
6. Reboot the LG G4
If after trying troubleshooting as described below doesn't solve your problem and clearing the cache partition doesn't either, you can try clearing app caches before resorting to a full factory reset. Do clearing app caches the correct way: Settings > Storage > tap Cached data > OK. Note: While clearing caches doesn't really hurt anything, cache files are there for a purpose and normally should be left alone unless you have a problem that you're fairly certain might be related to them.
With a little troubleshooting your phone can probably be straightened out without a reset.
If you have any installed, uninstall ALL task killers, RAM memory optimizers/boosters, battery savers/repairers, cache cleaners, antivirus, etc etc. None of that stuff is necessary. Such apps are actually counterproductive and some are just plain evil. They actually waste power and may disrupt critical system processes and degrade performance. Not to mention the nag ads many throw up.
Uninstalling crapware may solve the sluggishness. If the phone is still slow, install System Panel.
https://forums.androidcentral.com/e...ails?id=nextapp.systempanel.r1&token=Gn3WSQoj
System Panel makes basic trouble shooting of a sluggish device simple. Look at the opening screen, 1st one when the app opens. It gives the basic information you need. With the phone at idle (apps can be open, but nothing such as an active phone call or file transfer) check CPU and RAM memory usage (pie charts upper left corner).
Normally, CPU at idle should be less than 5-10%. CPU clock speed (top horizontal bar) varies but should be something less than max. RAM usage should be about 70-80%, unless you have recently rebooted and not yet opened apps to load RAM. You want to check these values after a fresh reboot, after some normal usage and when the phone has slowed. If CPU is high, look at the app list on the same screen. Check the CPU usage for each app (small vertical bar on left edge, next to app icons) for offenders.
If RAM usage is too high, again on the opening screen look in the Active Applications list. Check for a running app you have not used recently. It may not have closed or cached properly and is holding RAM.
If nothing seems unusual in the Active Applications, scroll down to Inactive (Cached) Applications. It may be harder to determine what belongs in this list and what doesn't, but if something looks iffy, particularly if it shows holding a lot of RAM, you can try long-pressing on it and select 'End Task'. If you select a required system process, no worry, it will just restart. If RAM usage returns to normal and/or the phone feels faster, that could be the offender.
Troubleshooting beyond this gets more complicated, but what is outlined above will find most problems causing sluggish performanc
Android since v1.0. Linux user since 2001.