Toyota Repair: I just bought a fairly used..., engine thermostat, toyota avensis

Question
I just bought a fairly used Toyota Avensis(2001). It 's a bit sluggish for the first 10 seconds or so whenever I start it and try to move. Afterwards, it's ok until I leave it parked for maybe 2 hours or so. This happens not just in the mornings but every time it's been parked for a while. Also, is it normal for the temperature gauge to be about half-way after only 15 mins of driving? It never goes past there though. Apart from these 2 things, it's a great car to ride. what d'you think?

Answer
Possible an idle speed control valve problem, it's located on the throttle body underneath, it can be removed and cleaned which usually fixes the idle and stumbling condition.
The temperature behavior seems normal, the engine thermostat is designed to bring the engine operating temperature up to normal as quickly as possible.