I dunno about Benzes, but GM uses window and seat motors with internal circuit breakers. If a switch stuck 'ON', the breaker would heat up, open, cool off, and close. The result is very much like you describe...a now-you-see-it, now-you-don't current draw.

Disconnect the battery and let everything cool off for half an hour or so. Then, when you reconnect, you might be able to hear where the problem is.

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1989 300 SEL that mostly works, but needs TLC