Problems with my dell Streak

i have a dell streak 5 which I had purchased almost two years ago. Since the past 6-8 months , whenever i connect it to my home broadband wifi, the phone switches off automatically and then goes into a repeat cycle of switching on and off till it hangs and I have to take the battery out and reconnect later after turning off the broadband. I had taken it to the local dell service centre also. they just uploaded the software again and said there is no problem with the phone. I am unable to so many things on the phone and It is very frustrating . I have deleted many apps but even then sometimes even when the wifi is turned off and i try to read on the kindle app or play a game, the same thing happens. Pls. advise.