The thing to do is to get the codes read and post them to the Prius Technical group. However, at 100,000 miles it's likely to be one or more of the following:
Spark plugs (about $12 each)
Clean the throttle body (about $15 from the Toyota parts department)
Clean the MAF sensor (See the instructions at
http://www.priuschat.com/)
12V battery is weak.