My Sony Tablet S has developed a gross speed problem. For the last several months it has run exceedingly slowly most of the time. Apps take 10's of seconds to start, taps to bring up menus take similar times, and more often than not I get a "Application is not responding" snag message to which I have to answer "Wait' to get the menu to drop down. I sometimes get spontaneous reboots when opening an app.
I used a Task Manager called Free Advanced Task Manager which shows the CPU usage.It varies from 15% to 117%. When It was indicating 117% there was no individual task with any appreciable CPU usage.
The tablet is not rooted, Android v 4.0.3 5a. Some apps on SD card, card (32g) is about half filled. Device memory has around 1G spare. RAM usage is usually about 300/750 Mb.
My question is: what are the likely causes for this and how do I track down the offender?