2.2 TiD starts 3 secs later stalls; next day normal

[Drankin]

I have a strange erratic issue, drove to work but pulled in to shops, tried to start the car, it revved then cuts out, if I try to restart straight away it just turns, leave it 5 secs, it starts then cuts out 3 secs later.
Got it towed to garage, hey presto no probs. Drove back to work 30 miles, no probs came to drive home 5 hours later same prob. Back to garage via tow.
Garage try car next morning, no probs. No error codes

Any ideas? Read lots about maf sensors ignition switch modules, ignition control modules,... But where to start. Garage not a Saab specialist.