Need some immediate help!!

Its been 3 years I'm using this router, no such problem occurred until now. From last 1 week, getting some huge ping spikes from my router. Can anyone suggest what should i do?

Things I have tried :

Resetting the router to factory default and reconfigured it.

Asked ISP for any issues from their side, but no luck.

Upgraded Firmware to latest version.

Need some urgent help, any help will be appreciated.