Touching wood can be little different from things like always putting the left shoe on first, and dismissing personal habits as "just OCD" isn't helpful.
We just don't think about every step of a habitual action, since it would be a waste of energy, and the human mind easily takes a bunch of movements and encodes them as a single action (analogous to a compter macro).
The origin of the habit may be superstition, shared culture, imitation or just personal practice, but it does not necessarily suggest any kind of belief. Of course, some people have superstitions more or less forward in the active mind, but even with these people something like touching wood is probably an ingrained habit rather than a conscious thought each time.
The habit may also have been filtered so that it is different from the original form - knocking your head as wood is an ironic version you've chosen, which may in fact reinforce the behaviour more strongly as "part of you".
The word "ritual" may be useful shorthand, but does have belief-related connotations.
I don't claim this as a scientific judgement, but I work on the assumption that we're all on the OCD spectrum; it's just that most of us are so far down to one end that we have few problems with it. Where exactly do you draw the line between "funny little habits" and a clinical condition?
Ed
