The next time it happens, note which bulb is out. Then inspect the bulb carefully and clean the sides of the metal base (ground contact) and then clean the lead colored point(s) at the very bottom tip of the bulb. Then clean the positive and ground contacts inside the socket that the bulb plugs into.
Sounds to me like a contact problem brought on by the dampness of a dark garage.
You can clean by scratching bulb with tip or blade of pocket knife or similar tool.
Also make sure ther is sufficient tension on the 'spring' contacts inside the socket.
[Edited by ejsharp on 05-03-2001 at 06:55 PM]
1993 190E 2.3
2000 Toyota 4x4 Tundra