The is an old MBK road frame from, I think, the 1980s. It was my main/only bike for a number of years but hasn't been used in about 10. I've treated it to a new paint job and new bits and pieces. The problem is it's almost unrideable, I guess because I've got so used to modern geometry. The steering feels slow and ponderous, but also extremely unstable at the same time. Standing in the pedals results in it going all over the place and I wouldn't feel safe riding it.
I can't figure out what makes it feel so odd. Perhaps the large fork rake and slack-ish head angle? Holding the bars on the tops rather than the hoods improves things slightly but it still feels horrible.
Maybe because the frames too small? It's also got a really short stem even by old road bike standards
If that's the right seat height for you then you're probably a couple of sizes away from the right size. Old school road had very little seatpost showing!
Stem too short that'll settle it a bit
Perhaps the headset needs replacing. I have an old Kona which wandered off all over the place. A new headset helped enormously, still a bit of a handful but at least predictable now.
If anything it feels like the stem is too long - my normal road bike has a 70mm stem, short reach bars, and the STI levers are shorter than these as well. I get a bad back if stretched out too far. I agree there's a lot of seat post showing! Maybe the geometry is just designed for people with short legs and long arms and body.