Internet is slow until I restart my modem..

Hey I just recently moved into my new house. I had Xfinity internet activated here. First off the service line isn't buried at all... But anyways my internet is slow talking 30mbs down I pay for 300. If I restart my modem router they provided it temporarily performs as it should, then bam back to 30.. I'd like to try everything I can on my side before I have a tech come out here? Any ideas? It's a single line going into the router no splitters just 3 barrels..