If the car doesn't drive what does it do for 20 minutes smoothly. If it only idles what happens when you put it in gear, what happens when you try to drive off?
If the accident had messed with the security system it wouldn't start at all. it could have affected other things. Does the fuel pressure stay constant when it goes from running smoothly to not at all.
Bosch Master, ASE Master, L1
33 years MB technician