I have an 01 IS200 with 98K miles on clock.

This problem only occurs in cold damp weather during winter.

After starting the car and driving for ten/fifteen minutes dash warning lights all flash on and off once. Immediately afterwards headlights go out and needles on dials all go to zero. Otherwise car contines to drive normally.When I pull in and turn engine off/on the problem is resolved and does not recur again on journey.

Car has been checked by main dealer and independent mechanics who can not identify problem.

Any suggestions?

take it to an auto electric specialist not a dealer or mechanic as they may not know. i had an alfa romeo once and the speedo pack,t up took it to alfa could not sort it.!!!! and local garage. so i phoned a mobile auto elec specialist he sorted the problem. had 3 diff elec feeds to it dam italian electrics lol.........

Possibly dry joint somewhere in PCB

I had a major 'cold weather problem' that is described in the (very long) thread:

http://www.lexusownersclub.co.uk/forum/index.php?showtopic=28384&st=220&p=707185&fromsearch=1&#entry707185

Maybe your problem could be related to this. If you find a solution, please let us know!