In 99% of these cases the crank position sensor is the problem. In oldere model with two locking tabs one on each side of the sensor for electric plug, Mercedes part number
A0031539628 Bosch 0261210141. I believe '98-mid '01.
Newer 01 on sensor with one connector locking tab is A0031532728 Bosch 0261210171. Just make sure you use OEM Bosch otherwise you will have to do it over soon.
you should be able to find them on internet for around $50 or at dealer for about $150.
These are heat sensitive when they get older and that is why when you let the engine cool off for like half hour you are able to start it again with no problem.
1999 ML320 230K miles
2003 Lexus GX470 285K miles
2001 ML320 162K miles
1980 280SE EURO W126 156K miles 142mph top speed SOLD
1984 300D TURBO DIESEL W123 SOLD