Huge lag spikes everyday at the same time

Hi everyone.

I'm one of those guys who just love to game the whole evening, but in the last couple of months, I have discovered a very annoying problem with my connection. Every day around 10:30 pm my latency spikes from 52 to 1500 ms. Sometimes even more. This happens for about 20 minutes before the problem disappears.
Have no idea what to do. I don't have any bandwith consuming planned for that specific time.
Btw. I live in Denmark

Have you contacted your Internet provider?
What type of Internet service do you have, DSL, cable, something else?

Also, scan for malware/viruses. Some phone home or send out spam emails at regular intervals.