What are signs of neurological disorders in dogs?

I have a 5 month Chihuahua who was recently neutered. Since his surgery he has been having these episodes where he bites at the air and at his hips. Sometimes it is triggered by a noise other times it happens when he is just relaxing. He usually gets scared when this happens and runs to his crate. Is this most likely neurological or could he having pain in his hips?

Neurological disorders are usually easy to spot,ie-tremors-seizures-blown pupils-while walking the gate is off and most times the animal will be very scared and could bite strangers as a result.appetite will usually dwindle in serious cases.I would check his coat for lumps bumps.Next check the analsacs to see if they are full.It sounds more like anxiety,hemay have gotten spooked.Check for fleas or mites,chiggersExamine the hips closely.if it persists it's off to the vetsExamine his bedding or immediate enviroment-he couldhave an allergy to a host of things.If he exhibits any veryextreme behavior bring him to the vet.Puppies are veryvulnerable and should be treated ASAP when there is areal problem.But don't freak out till it's called for.I have a5month old terrier so I know how tedious it can be.ITs a long shot but look in his ears see if they are cleannotice any oddities he may have,do not attempt to cleanleave that to a vet ear mites in pups is common.Chances are he is just new to his surroundings.