Interior light/door lock problem 1999 C280

When I get in and close the door the overhead light goes out, then as I start to drive the doors lock. This is normal. The problem is that as I drive along the overhead light will come on and the doors will unlock.
If I then push the overhead light switch the light will go out and the doors will again lock.
When I turn the key off the doors unlock automatically as normal.
On a long drive this unlocking can happen several times (perhaps every 15 minutes). It seems to happen completely randomly.
Any ideas as to the cause or how to fix this?
Thanks, EJ in NJ
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I would start out by changing your driver door switch... maybe internally, there is a fault that when you hit a good size bump, it will trigger the light on.
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you may be able to quickly test this by taping a penny directly across from the door switch/plunger. close the door and the added thickness should depress the switch more deeply. if the in-motion anomalies abate, it may very well point to that switch as the root cause. fortunately, it only about a $20 part.
yes, the road undulations will wiggle to door and change the pressure on the door switch, already teetering on the brink of inoperation. the door/switch thinks the door is opening, thereby triggering the open door features: unlock the door mechanism, and turn on the interior lights
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