Car Oversteering And 'floating' Like Sensation When Driving Ov

[wren111]

Hey-I'm new:)-Hope this is the right section. Ok...

My 1998 avensis's steering feels really loose when turning bends, in particular, when turning left over 50 mph on a downhill curve on the motorway(it's now started doing it when turning right on a bend too).Downhill driving at high speed gives the car a floating like sensation as if it's not gripping surface(tyres seem ok). Also,when pulling in to a lane on left, and to a lesser extent right, on motorway at 50 mph and above, it feels like the cars going to swing right into the next lane or the backend will turn.Esp in wet weather.! In addition,when i go over an uneven surface on the motorway for example at 50 mph and above ,the steering is moving in my hand to an excess and the car jolts too much from left to right

I've shown it to the mechanic he said it's nothing, just because the cars old.I'm not convinced 'it's nothing'. I need the car for work, but this is starting to create anxiety when i drive.I have to drive over that awful M62 to Leeds at time & down to London alot too. I'm normally fairly confident at driving. Any sensible ideas on what it might be? I was researching and from what i worked out it could be the suspension? I don't know much about car mechanics, so any help world be great. Thanks.