2000 Chevy S-10 Won't Start

Engine Mechanical problem
2000 Chevy S-10 4 cyl Automatic

Have a 2000 Chevy s-10. Purchased new. Has 100K miles. Has long history of periodically won't start. Turn the key and nothing happens. Usually after 5-10 times in repeated tries will start. However, no longer working. Last week had it towed, after 5 days ( at least 20 attempts per day) of no starts. Mechanic turned it on. Now working. "Started right up" They state can't diagnosis problem since vehicle started. Perplexed and Confused. Help!