Make sure you are using the proper AC adapter. If your PowerBook 180c has a modem and a large RAM card, it may require more power than most AC adapters provide. The PowerBook 180c requires a 24W AC adapter. The proper Apple AC adaper can be identified by the Model number M5652, and reads 24W on the AC Adapter tip. If you are using any other AC Adapter and your battery is low, then your PowerBook will not always startup properly without a fully charged battery.
Note: The model M5652 adapter has been replaced by model M4662. Either adapter will work properly with a PowerBook 180c.