Robin acting strangely

A friendly robin in my garden has been acting strangely. It appears to be trying to rid itself of perhaps fleas or some other irritating thing, it also lay prone for several minutes before starting again the previous actions. It resembled what I witnessed a swan doing when it left the nest after incubating signets but this robin had been around the garden for the last few weeks. It looks heathy and still comes to feed and drink but should I be concerned?