I'm not living in the area now, but I spent a lot of time hiking this area when I did. The copperheads are all over the place. Several people have reported stepping on or almost stepping on rattlesnakes. Copperheads are not as likely to rattle as the timbers. Copperheads prefer to sneak away rather than stand their ground. However, Coppers (like any large snake) will resort to striking if cornered. The timbers are more unpredictable. They might rattle, they might sneak away, they might grow aggressive, they may remain indifferent. You are all wise to wear long protective pants or high length boots and suitable gloves while caching.
From what the OP has said, it sounds like a timber to me.