Gonna nod off while at work, could this be symptom of narcolepsy?

Possibly: One of the main symptoms of narcolepsy is excessive daytime sleepiness. However, daytime sleepiness can be due to many medical causes. A quick screening test is the epworth sleepiness scale and can be found at: http://www.Stanford.Edu/~dement/epworth.Html. If you score a 9 or higher, see your doctor and explain your concern.

Could be but ...: Could be but generally this could be a symptoms of many other things as well. People often fall asleep actively engaged in activities with narcolepsy. So it may or may not be sitting at computer at work, particularly in the afternoon. If this is recurrent, see sleep professional.