320i 1988 reg, 110.000 on clock. Start up fine, then 5 or 10 mins later car stops dead. No sudden jerks, spluttering or missfiring it just stops dead. Ignition is still on and all lights still working. Sometimes it will re start as soon as I turn the key and other times I have to wait a few minutes. This has happened whilst on the motorway so I have had to coast it onto the hard shoulder, throw it into neutral and try to start it whilst still coasting but it will not start this way so I have to stop and wait a few minutes. I have also been approx 20 to 30 minutes into my journey when the car suddenly cuts out and then comes back in seconds as though the ignition is switched off and then back on. Also if I rev from a smooth tickover 850 ish, quick on the pedal or from under bonnet, the revs drop to a near stall and then picks up and is fine. This is the same if I try to drive it, I have to keep the revs high to pull away. Any help would be greatly appreciated.