Pre-flop range is massive.

Flop check/call, then check on the turn, looks like he's chasing a draw - probably a flush draw given two spades on the flop.

Bet on the turn is only 35% of the pot and I think it is either a weak attempt to steal the pot with a busted draw - small pair or air - after seeing you show weakness by checking behind on the turn, or he has a J.

After 125 hands with him I'd hopefully have some sort of read, so if I thought he was stealing I'd obviously call (or raise?), but if I thought there was a more than 1 in 4.5 or so chance he had a J then I'd have to seriously consider folding. With no read, given the size of the bet I think there's a reasonable chance he's trying to get you to call, so I'm leaning towards a J. Which means fold.