if both of Andrew's tests pass, a third test is to check your DNS server is responding.
This really depends where in the webpage loading sequence the stuttering is happening...have you noticed whether your browser stalls at "looking up [webpage name]..." or "connecting to [webpage name]..." or maybe "waiting for [webpage name]" or "transferring from [webpage name]" ? These are firefox labels, Chrome seems to just have "sending request" and "waiting for" which is less useful.
If the stalling is during the "looking up [webpage name]" stage then you could have an issue with DNS servers. I think TT may have an issue with one of theirs... 3 weeks back a family friend on opal had some issues which seemed to be fixed by switching to 18.104.22.168 (google DNS).
To test the DNS server:
In a similar command prompt/DOS window type nslookup and press enter
This should connect you to your default dns server and leave a > prompt
type a web address for example www.heb.com
and press enter
you should get back a "non-authorative answer" and an IP address for that website
When your internet is misbehaving try a few NEW websites in here. I recommend any 3 letter site because you can make them up and nearly all are real eg www.abc.com www.abd.com
If you are not getting fast answers (less than a second) then this might be the cause of the stuttering
In theory, theory and practice are identical.....in practice they aren't!