car started this morning , turned it off then would not start(good battery) left it alone about 20 in and again would not turn over,seems like im getting power to starter

basicalyy the wife went to work stopped and got gas and got back in and it would not turn over ,tried jumpstating thing possibly the battery and nothing ,so I ran her to work came back 20 min later and all of a sudden it started kinda barely, but got it home when i got home shut it off and once again would not start, has full power battery checked out and I did crawl under to see if power was going to the silinoid and yes it sparked thought I could cross over that maybe the silinoid was just not kicking in but that old trick didn't work, so I.m thinking stsrter is there anything else that would cause it to not start ,then start, and then not start again