I Just Had An "attack" Of Extreme Weakness In Both

I just had an "attack" of extreme weakness in both lower extremities. Along with weakness is a sensation that feels like "urgency" that is also experienced in the buttocks/rectum. Legs felt rubbery and at risk of collapse. I held on to the counter for a few seconds then walked carefully to the couch. Sensations subsided within 5-10 minutes. This has happened before at a rate of a handful in a year. Please respond. Thanks.