Cottage hill bill

Started the Suburban this morning, no issues. Drove about 20 minutes and parked. Walked around for 30 minutes and got in to leave. Absolutely no electricity. No dash lights, turn key, no click no noise, nothing. It was as if there was no battery installed. Called wrecker. Sat for 5 minutes, opened hood, lifted cover on positive battery terminal, closed everything, got back it truck and it started right up like normal. Drove home. Have started truck several times since, no issues. Testing between positive terminal and ground on hood brace, voltmeter shows 14.45 volts while running. Any ideas?