More info is needed. After you register and can reply, we need to know a few things.
Phone make and model? (Some are worse than others for this)
Do you still get the charging notification when this happens?
Is this a complete halt of charging, or is it just really, really slow?
Is this any time you use the phone, or do certain activities influence it more than others?
Are you feeling excessive heat when it happens? If so, where?