OK this is my problem 1988 E30 M3, 104,000 miles Sidewinder alarm system (this may be the problem) From time to time starter will not engage--car won't start. All dash lights come on, fuel pump,etc. all work engine won't crank over. Some whirring sound and soft click from engine bay but no strong engaging noise from starter. Then after many tries and cyclling the alarm (off, on ,off) try restart still nothing. Then just as strangly try the next day and it starts right up. No predictablity. Battery is good and about 4 months old. AAny ideas or similar problems? I'll take best gueses at this point. Thanks in advance.