My 2002 Volvo S60 2.4T with 93,000 miles is in the shop again -- 3rd time in a year because it randomly will not start. I appreciate any ideas!!

Description of incidents:
1. Last July -- went to lunch on a very hot day. Returned to car and it would not start. Thought I seriously forgot how to start a car. AFter waiting about 20 minutes, the car started. No messages. I took it to the shop and they said they downloaded new software.

Note -- Certified warrenty expired in March

2. May -- drove home from work and ran inside. Returned to the car and it would not start. Left it parked and tried again 2 hours later and it started fine. No messages. Took it to the shop and they couldn't reproduce it. Told me to call if it happened again.

3. August - This week -- car wouldn't start after having dinner at a restaurant. For the first time, the "IMMOBOLIZER" message showed up. We opened the hood and the car started within 15 minutes.

4. August This week -drove car to grocery store. Car wouldn't start; Tried all 3 of the keys that came with the car and none worked. No messages this time. Called shop and they suggested replacing the battery. Tried to jump it, but still wouldn't start. After having the hood up for 40 minutes, it started.
5. August - same day... drove the car home. Tried to immediately restart and it once again failed to start. No messages, just a very expensive garage ornament at this time.

What to do? The car is in the shop again, but they can't reproduce it. Wondering what they will suggest. Has anyone else had these experiences?

I have a good friend that has a 98 s80 with a very similar problem. At about 130k miles, he put his key into his car one day after work and nothing. It would turn over but kill immediately. After a while it stopped turning over.

Took it to the stealership and they said that the immobilizer had been activated, and the car wasn't recognizing his key. They replaced the key, updated the software, and worked with the immobilizer. he paid ~$800 for the whole works.

Update...

Dealer couldn't reproduce the problem. They drove it off and on for 3 days and did a hot soak (not sure what that is). At this time, I have instructions to call when it happens again. The starter is not getting power on these random occasions. Without knowing for sure the source of the fault, we are going to wait it out before replacing parts.