2000 Buick Regal car wont start sometimes in summer

My car was acting up last summer not wanting to start, it turns over but kinda acts like its out of gas, sometimes if u wait a bit it will start right up. Sometimes it will die going down interstate or just driving thru town. Then winter hit and no problems all winter. Now its summer and we are having problems again! Everyone has suggested fuel pump but you can hear the pump working. I have done some research that maybe it might be main relay or fuel regulator. Would it have something to do with ambient temperature and what within the engine has problems because of the ambient temp? Please help