lately my car seems to start up really slow. It sounds like the starter is having trouble turning the engine over, but eventually it starts.

I put a new battery and alternator in this summer and havent messed with anything when it was starting normal. Does this sound like the starter is on its way out? Should I just replace it?

 

Could be, however make sure the cables are OK. A cable can look OK but be corroded as hell inside. Check the battery ground cable at the block, clean if need be and ditto for the positive cable going to the starter solenoid. If it does it more when hot you could have what they call "heat soak". The starter because of all the crud it accumulates tends to bind up when hot. Many times just disassembling it and cleaning and relubricating will correct it. if you replace the starter stay away from the chain store ones, try to get a Delco reman. It's worth the extra coin in the long haul.