Bearings can get loose over time (that's not many miles over the years).... anyway, if you want to check the head bearings, just get the front wheel off the ground ~ I'd suggest the bike on the center stand and someone (or something) on the back to get the front end in the air. Then just grab the front wheel and pull it forwards, and then push it back. If it moves, then there's a bearing issue. Could be that they're just loose, or maybe bad (which is a different check).
Anyway, something simple to check... just to get you started down that path if necessary.