ants in the pants

[Theseus]

(Humorous) to be very restless or excited about something/not to be able to keep still because you are very excited or worried about something
--She's got ants in her pants because she's going to a party tonight.
--I wish he'd relax. He's got ants in his pants about something today!
--I've got ants in my pants - I can't wait to get started on my experiment.:up:

 

[Palavra]

You can say κάθομαι σε αναμμένα κάρβουνα (I'm sitting on blazing coals), i.e. be very anxious about sth, really look forward to sth etc.

You could also say έχω καρφιά στον κώλο μου. However, κώλος is the equivalent of arse, so if you want to tone it down, you might say έχω καρφιά στον πισινό μου (my butt), but this mostly means that I can't sit tight, I'm restless and need to be doing something all the time - I feel it's not an exact equivalent.

 

[nickel]

Quite similar to κάθομαι στα καρφιά also.

 

[oliver_twisted]

And also
Δεν κρατιέμαι
when one can't stand still cause they're very excited

 

[drsiebenmal]

The κώλος/πισινός phrases can also be paired with νέφτι (terpentine), usually in the 3rd person: Πώς τρέχει αυτός, σαν να του έβαλαν νέφτι στον κώλο.