hi, i have recently bought a 1999 xj8 3.2 sport and the steering is very heavy, ive driven xj's before and know the steering is light when manoeuvring and tight when upto speed. my steering is very heavy and sometimes difficult to park with. now tonight i got in after not using the car all day and the steering was lovely and light and was spot on. i then turned the car off and left it for about half an hour, came back and the steering went light then heavy then it decided to go light and heavy at the same time and was difficult to drive, by the time i got home the steering had gone back to heavy again.
what the hell is wrong with my steering??
please help someone!

mike