Raheem Sterling put City in front on 22 minutes before Jetro Willems equalized but Kevin De Bruyne looked like he had won it when he smashed in a second off the underside of the bar eight minutes from time.
Shelvey's equaliser presents Liverpool with a superb opportunity, with the Reds potentially being 11 points clear this evening.
They were fortunate to beat Chelsea 2-1 last week and before the worldwide break struggled past a Southampton side crushed 9-0 at home by Leicester City.More news: Malta PM to step down over slain reporter case
Guardiola's City broke numerous records as they clocked up 100 points in winning the Premier League in 2018 and followed up by claiming a domestic treble last season.
One win in their last five games in all competitions is a worrying statistic for Guardiola, who can only hope that cracks finally start to appear in Liverpool's armour in the busy month ahead.
Pep Guardiola has declined to comment on suggestions that assistant manager Mikel Arteta could be a candidate for the Arsenal manager's job. "I know that we can't lose any", Guardiola said. "We found a way today but at the end we conceded a goal".
"Sometimes it happens. The tempo was good all the time". There is not just one thing - it's one thing and another that helps us to be more solid as a team.More news: UNC comeback falls short against MI after fatal second-half cold stretch
"We have to accept it, work on our strengths and learn from this".
"I might be a hero in Liverpool now but in all seriousness we need as many points as we can and we need to keep moving up the table".
Defender John Stones said City had gone from "elation to deflation" on Saturday, but insisted the race was still on.
"For me myself, I want to see my players and the reaction of my players and everything", Guardiola added.More news: Africa to Play a Big Role in Bitcoin Revolution: Square CEO Dorsey
"It's still on because we will still fight until the last day like we did last season. The spirit has to be there".