Just bought a Stilo and it ''wobbles'' between 40 + 50mph, once you get past that it is fine, do not think it is a problem with wheel balancing, guy l bought it off said he was told it was prob the drive shaft but does not make much sense to me. l know the front shockers are shot, could that be causing it?
A mate of mine is a mechanic and he is had the wheels off, reckons they're alright. asked him to balance them but he has not (useless) so will get them done this weekend. Cheapest thing to try first!

wheel balancing or the wheel itself id be leaning to the balance if it only happen at one speed.. and shocks dont vibrate they bounce and it could be the shaft but id have the tires check first. is more common

Check the wheel balancing first.

the drive shaft can be to blame if the hub nut is loose. could also be the shocks they maybe dry & not show signs of leaking but this doesn mean they r anygood & that is all mechanics look for now adays including MOT's. could be the tires there selves rather then the balancing can also be a buckled wheel. could be the tracking, could be the bushes, could be the balljoints, beaings it could even be a bent strut. the list goes on mate l recon u should have the wheels put on a balance machine if they need anymore then 5 grams putting on them or if buckled then there is the problem if not then u need to have the suspension thoroughly checked by someone that works on italian cars because not all mechanics no what there looking for, then it needs the caster, camber & toe checking