Internet won't work for a long time after booting up

Hi
After I boot my computer I cannot connect to the internet for a long time.
The resource monitor shows svchost.exe (Network Service) running CPU at a constant 25% and disk is often maxed out and plenty of hard faults
If I try to open network and sharing it will mostly fail - white screen with blue spinning circle and that will often cause windows explorer to restart - all icons and task bar disappears then reappears.

If I leave it then come back in 15 minutes or so it will have sorted itself out and svchost CPU use is down to 0

Any suggestions it is really annoying.

I had a similar problem, this may help you..... I found it useful.

What is svchost.exe And Why Is It Running?

Thanks for your reply. Read with interest.
DNS Cache is taking the full 25% of CPU. Tried restarting but doesn't make any difference. Eventually the CPU use will drop to a low % then everything will start to work including internet. Not sure what to do now.