Netgear C3700-100NAS drops mps over time rebooting fixes for a couple of days.

I have the above cable modem firmware version 2.02.22, which was upgraded by Xfinity when I started my service with them. I am signed up for the 100mbps package. When I do a speedtest I will get a varied response, usually well under 50mbps. When I reboot the modem, the numbers go up to above 100mbps, but it does not stay. I have had this service since Tuesday, and have had to reboot the modem twice. Attached is a list of the recent speed tests. I did not keep the others from the past rebooting of the modem. This is not the version2 that is what xFinity has on their list. Any suggestions or ideas as to how I can keep my signal consistant? Do I need to look at getting a different cable modem? TIA.

I tried to upload an image showing the speeds but seems that did not work. Here is the info: Speedtest 2 days ago download 32.70 mbps upload 5.86 mbps, Latency 18ms. Speed Test today: download 37.92 mbps upload 6.03 mbps, latency 18 ms. After a reboot of the modem: download 119.79, upload 5.88 mbps, latency 16ms. This is about the same that has been happened since xFinity install last Tuesday.