I wouldn't worry about it.
It's just vibrating at idle because the a/c compressor is kicking in putting a load on the motor and the rpm's are dropping slightly.
The every ten seconds approx is just the compressor cycling on/off.

Just drive it.

first thing's first.

1: when was the last tune up?
2:how old is the a/c compressor? factory?
3:check the mounts.

if the motor mounts are bad put the thing in N-Neutral and rev it. if the motor moves 1 mount is bad. now put it in R-Reverse and rev it if it moves that's bad also. now i may have it wrong some. but if u rev it and the motor moves you have bad motor mounts.

the only reason i ask about the tune up is. it could be a misfire and just happen to drop in rpms when the clutch kicks in.