Suggestions for a timer for a shop heater
Not possible. Trendy pushbutton timers require neutral, and you don't have it. Wait.  You're old-school, and you want to use an Intermatic wind-up timer where the energy comes from YOU? Oh yes, that'll work just fine! 

No  . . . 
Yes 

In fact, that's exactly what I did with a water heater.   Now, the timer might be rated for the amperage.  But I didn't take any chances; I used a 240V relay.

Mind you, I used a relay intended for an air conditioning compressor, and that is not Code legal, because that relay was not application-listed for a water heater.  But if you can find a relay that is listed for your purpose, or a general-purpose type like a RiB, then you're all set.  

There are also the Aube relays with transformers built-in, which provide 24V pilot voltage, so you can do the wiring from relay to timer with low-voltage thermostat wire.  

And if you're thinking "24V! That means I could use any 24V thermostat, even the Nest!" you're almost right.  Depending on the model, Aube's transformer may be too little to power the Nest, but you could use separate transformer + relay, or a relay-transformer that's a little bigger.  I've even seen transformer+relays that mount on junction box lids.