In general the use of statives in the progressive voice is at least clunky, if not downright ungrammatical.
Over the last 150 years or so, however, this use has been growing with some statives, though not all of them. It 'recategorizes' the stative as a process verb: an activity verb like study or even a telic verb like learn. Usually this is done to imply either that the 'state' involved is temporary or changing or intermittent, or that it requires some active participation on the speaker's part.
- I'm seeing better with my new glasses.
- I'm understanding more and more about modal verbs.
- I'm not liking Ed nearly so much as I used to.
- I'm thinking how we can drain the basement.
In the case of wondering, you can probably figure out from context exact what is meant. For instance,
We typically say "I'm wondering whether I might..." to imply that our uncertainty is a temporary state which we expect the hearer to resolve.
We typically say "I've been wondering that!" in response to another speaker's announcement of some fact the speaker obviously expects to be interesting. The response flatters the speaker by implying the matter is in fact one you have been taken an active interest in and that you are grateful for the enlightment provided.