E430 Intermittent Starting

[GParker]

My '99 E430, 58K, very well maintained decided to not start... again.

When key was inserted, the usual dashboard "relay" sound before the key can be turned was different. Instead of a full "click" I get a bit of a muted click or thud.. and can't turn the key at all. Tried both keys several times. Two hours later it starts fine for road service, making me look like a capital "L" loser. Road service mumbled something like the weather may have caused it.... inside my garage!

Dealer says "I dunno".. perhaps anything from key switch to (insert fancy name here) computer module costing $2300. The battery was replaced just two weeks ago in a probably unrelated, dissimilar no-start event.

My choice is to see if this happens again and strands me, or head to my dealer for perhaps nothing-to-find diagnosis. Advice appreciated.