So I took off today from home and shortly thereafter just about all my dash warning lights lights came on, except for check engine. Running fine otherwise. Went back home, checked oil level - ok, checked battery - 12.86 v, so I decided I had a loose connection. While driving, I notice that the lights would come off and on as I hit bumps and rough road, eventually staying on. I drove about 25 miles and had no problems restarting. Came back home, and when I went out to start it again, it cranked weak, and then the starter clicking sound. I just had a mechanic tell me recently he recommended a new battery. Does this sound like a battery problem or is something loose? I checked the posts on the battery and they're clean and tight, although only after I tightened the negative terminal after the fact.

Any thoughts?