my p reg vectra keeps cutting out?

I have a p reg 2.0 vauxhall vectra. I battle to start the car but after i have started it it wil cut out after about 2 minutes and then it wont start, i have to wait about 2 or 3 hours and then it will start again. When it does start again and i rev it, the revs wont go over 4.5 even with the accelarator right down.

i am baffled