I have owned an 850 for 2 years, had an intermittent problem starting, no real tie in with anything, weather, trip length, etc (although at times there seemed to be a link to trip length, auto door locks, etc). Would start, then not start (got nothing, dead silent). Bought the car from a lady who had taken excellent care of the car and had it in to Volvo Dealer on numerous occassions trying to get the car fixed. Dealer replaced the starter twice, starter switch in the column three times, and various other parts/sensors which the computer said were bad (throttle position sensor, Mass Airflow Sensor, both oxygen sensors etc). Finally she gave up (many thousands of dollars poorer)and I bought it for an excellent price. I Thought it was the security system relay, or PNP switch(which the dealer had replaced). Sometimes I would just hold the key in the start position and eventually it would start (one time over three minutes)sometimes it would start if I locked and unlocked the doors. Occasionally, alarm system would activate without reason (horn and lights). If I disconnected the battery once a week and left it disconnected for an hour or so it would not have any problems starting. The problem was one of the ECUs (the A unit which controls engine timing, fuel mix, etc). Card is approx 1,000.00. I put up with the problem for longer than I should have because of the cost of the card. Dealer never will find the problem, because when they connect it up to their test equipment whatever defect is in the card is "temporarily" corrected but other parts report back as bad (because the ECU is faulty). Hope this info helps.