Yes, Martin has nearly 60 fantasy points in the last two weeks. Yes, he's the No. 3 ranked running back on ESPN. And yes, you should sell him while he's hot.
Martin has looked like the muscle hamster of old the last couple of weeks, but match-ups against a Panthers D/ST without half its linebacking core and a Jaguars D/ST without it's best player will do that. At the very least Martin has solidified himself as a RB2 in most cases, but a rough Tampa Bay defense and the always hovering Charles Sims likely keeps him from RB1 prospects in the long term.
That said, if you can get RB1 value for him, and you likely can, it may not be a bad idea.