A 51-year-old South Boston man who has been convicted nine times of operating under the influence has been arrested again on drunk driving charges, Suffolk District Attorney Daniel F. Conley said. Timothy Davidson was arraigned Monday in Boston Municipal Court on charges of operating under the influence of alcohol as a fifth or subsequent offense, operating after suspension, and leaving the scene of an accident causing property damage. A not-guilty plea was entered on his behalf, prosecutors said. Prosecutors said Davidson was intoxicated while speeding at 7 p.m. Saturday when he struck the car of a 48-year-old Rhode Island man at an intersection in South Boston. That driver was not injured.