Sometimes, Nokia phones have the problem with a few apps or programs, and there are errors which can not be closed down, and the apps keep running with the errors. Resulting in slowing down of your mobile phone. Many people take it as a problem with phone virus, and try to just check for that.
But you better can reset your phone once to make the confirmation that it was some app error which was the reason for that slowing down of your phone. There are 2 options for resetting a Nokia phone –
Soft reset just brings you back to the basics. It takes your Nokia phone to the initial stage or Factory settings that were given when you bought the phone. To make a Soft Reset –
Press *#7380# in your Nokia phone and if you have set a security code, type that when asked. The phone reboots and soft reset is done.
Hard reset is needed when the problem still persists and you might need to remove the apps and errors from their roots. To make a hard reset –
Press *#7370# in your phone and follow same thing as above.
The hard reset deletes every app that you stored in your phone memory, along with your contacts. So you should backup everything before you proceed with that.