Hotpoint Aquarius Condenser Tumble Dryer Model TC71 stops after a few mins?

Hi Push button and it starts OK - rotates, reverses and have heat but then stops. The push button will NOT restart it unless you keep the button depressed and then it will run as long as your finger is pushing button in. The push button start will not work again until the machine has stood idle for a time and if I push button start again it runs for a few mins and stops when the relay switch opens for no apparent reason. What does this point to being faulty.... the relay? or the pair of little green spot thermal wotsits that sit above the heating element .... or something else. Appreciate any advice. Thanks