Some background information would help us out.
Are you rooted? If so, what ROM are you using and how did you restore your apps?
If you are not rooted, then when was the last time that you power cycled your phone? You could also try removing the battery (after shutting the phone off) for ~5 minutes, and then see if that helps.
A final method (though it will erase all your data and settings, but since your contacts and calendar items and such are synchronized with Google account, it is not *too* bad) would be to perform a factory reset.