SAAB 900 engine cuts out

I drive a 1999 Saab 900. Sometimes when I have driven about 10 miles the engine simply cuts out and won’t start again. After about an hour on a cold and frosty night, the engine will be able to be started again. Any ideas what could be causing the problem

Has it received all the recommended maintenance? Does it do it all the time or just occasionally?

Yes, the Saab dealer has carried out the annual maintenance every year or less depending on the mileage of the year. It has approximately 180,000 miles on the clock - original engine, clutch, manual transmission etc. It only seems to do it sometimes in the last week it has happened 3 times, each time at about the same distance but there have been 3 days when it hasn’t happened although I have driven more than 10 miles.