Learn English – Idiom: A person who is unfolding truth, changing statements during the conversation

I don't know any relevant idioms, but unvouched-for would be understood by all native speakers. Depending on the exact context, maybe uncorroborated, or unsubstantiated might fit better.

Fidgeting covers a wide range of nervous, almost unconscious, movements of the fingers, hands, arms and legs. It would also be used to describe what I'd call bouncing leg motion that sometimes occur while sitting down. It's not usually a sign of a medical disorder, in fact, if you make the person aware of their nervous "tic" they usually stop; until they forget, and then they'll start over again.

Nervous energy is also another term which might be the proper translation for binboyusuri

I found a few forums on this phenomenon but none had a proper "name" for this action. The Friends and family forum had a post on this condition.

When I am sitting down, I constantly "bounce" my legs, up and down vigorously, to the annoyance of my workmate next door to me as her workstation shakes madly! I also do this at home watching TV or just relaxing and I've done it ever since I can remember. I don't believe it's "restless leg syndrome" as I always sleep like a baby, although I do tend to toss and turn a bit as early morning approaches.

Men's Health has a small article on this subject, and includes a helpful tip on how to stop "jiggling" your leg.

It's probably just a nervous habit that may reduce stress or anxiety, says Raymond Miltenberger, Ph.D., director of the applied behavior analysis master's program at the University of South Florida. "Or maybe you're simply bored," he says. It may be a benign tic, but it's a highly visible one. At best, you look nervous; at worst, people will think you're about to rob a bank. To put an end to this involuntary jackhammering, Miltenberger suggests putting change or keys in your pocket. If you hear jingling, that's your cue to cross your legs, hook your foot around your chair, or stand up.

Edit:
Wikipedia seems to confirm the description "bouncing leg" in its article on fidgeting.