Danny Briggs finished one shot off the lead at 7-under-par 64. He was followed by Jeff Sanday, Anthony Rodriguez and Eric Johnson, who share third at 6-under-par 65.
Restino burst out of the gate with four consecutive birdies starting at the par-3 second. He found trouble with a bogey at the par-4 sixth but regained his composure with a birdie at the eighth to make the turn at minus-4.
The 39-year-old continued his fine play on the back side with back-to-back birdies from the 10th. Restino then closed his career-low round in impressive fashion with birdies at both the 17th and 18th holes.
Restino has had an inconsistent season thus far with eight missed cuts in 14 starts. He held a share of the lead after the opening round of the Canadian PGA Championship in June, but went on to finish in a tie for 36th.
'My sponsor told me to start looking for something else to do, so maybe that was a wake-up call,' said Restino. 'I guess I could either get a job or keep playing golf. But lately everything has been getting real good.'
Restino's game has improved over the past three weeks with three cuts made, including a seventh place finish at the Oregon Classic.
'You know, I've been feeling really good lately,' said Restino. 'My confidence is really high right now and today I played pretty solid.'
Jason Buha, who won this year's Dayton Open, was three shots off the lead after a round of 66. Buha was joined by Richard Barcelo, Doug Garwood, Joel Kribel, Ryan Howison and Ernie Gonzalez in a tie for sixth.
Mark Wilson, Chip Beck, Patrick Sheehan, Shane Bertsch, Tjaart van der Walt and Andrew McLardy share 12th place at 4-under-par 67.
Jason Gore, who captured the Oregon Classic and the Boise Open in successive fashion coming into this week, collected five birdies and three bogeys to finish six shots off the pace in a group at 2-under-par 69.
Defending champion D.A. Points, who is trying to become the first player to successfully defend a title on the Buy.com Tour, carded a one-under 70 that featured two birdies and one bogey to finish seven shots off the lead.