1996 BMW 318 Car shakes or vibrates

With the info provided it is tough to get an idea what could be wrong. Have you maintained the vehicle? When did this issue start? Has there been other outside influences? Tell me more about this thing you feel when driving, is it in the body or in the performance or what, what kind of noise is it? It could be the driveshaft center support bearing carrier has failed, if I had to guess.

Hi.Many thanks for your prompt reply.I will try explain things best I can,so it may help you build the idea whats wrong.
From mileage you see this car has been used quite a lot,however,I am only second driver to use it.Its a petrol engine.Have used it past 3 1/2 years and has run smoothly.Last 2-3 months car started doing this,however rarely.But last 2-3 weeks this is happening every day.When I start the engine and leave it idle,I can feel some vibrations on my feet on the carpet and on the front seat.Even when I accelerate and then drive,vibrations continue.Kind of aggressive engine and I think more noisy than a normal driving.Because my car is automatic,it does take a while for gear change and this is when vibrations are felt mostly.One idea I had was the engine mount problems,but I wont go for repairing it since aint sure thats the problem.
I wouldnt say I have spend quite a lot maintaining this vehicle,but just bits and pieces,oil change,mot,etc,but not major services.
I dont think there may be other outside influences,i.e.loose screws,etc.
Any more explanations needed,please feel free to ask.
Thank you again.
Cheers.