- To be coherent or intelligible:
an explanation that made sense.
- To be practical or advisable:
It makes sense to go now.
"to make sense" means to be logical, intelligible or reasonable. Your example should be "People sometimes make sense". As a complete sentence, this is a slightly unusual thing to say because experience shows that most people are reasonably logical and intelligible for much of the time. It could be used with a touch of irony, but one would need more context to judge.
Some more examples:
"It makes sense to get professional advice."
"Ah, so I should have added rather than subtracted. That makes sense."
"It tells me to click 'OK', but there's no OK button to click. These instructions don't make sense."
"He tried to explain his theory to us, but frankly he wasn't making much sense."
You can also "make sense of" something, meaning that you manage to understand it:
"I can't make sense of these instructions."
"It took me all night, but finally I made sense of these accounts."