HAVANA — Cuba began to slowly restore power on Monday after the country's national electric grid collapsed earlier in the day, the latest blow to an island already suffering from severe energy, fuel and medicine shortages. Grid operator UNE said it was providing electricity to some vital services, including hospitals and food production centers, but by late afternoon was able to serve only 1 percent of the capital Havana's demand. Officials have not yet said what caused the grid to collapse. Cuba has for months suffered from hours-long and, more recently, days-long power outages linked in part to a decrepit grid and a U.S.-imposed oil blockade that has cut off the island's fuel supply. The nationwide outage and slow recovery are more bad news for Cubans already exhausted from rolling blackouts that make it impossible for many to work or sleep in the Caribbean summer heat. "Look at my face, it says it all," said Ariel Sotelo, a bleary-eyed 57-year-old Havana resident who had been without electricity since the day before. "We just have to grin and bear it, but it's not easy." Nearly two-th