Freezes every time

i have had my new xbox360 premium for 4 months and never had a problem. Lately, in the last month, the xbox makes a real bad sound until it warms up after about 30 seconds.  But now, in the last 2 days, within 5 minutes of starting it up, it freezes every time. The only thing i can do at all is manually restart it.  Never had a red ring.  I also have a NYKO intercooler that i put on after i owned the 360 for 1 month.  I have also emptied the memory cache to no avail.  What do I do?