PolkaDotMom is certainly correct to point out that cervical fluid is THE MAIN signal that ovulation is approaching. There are other signs that can be used as cross-checks, such as cervical position, vaginal sensation, etc., some women have a little spotting around ovulation...there's even a lymph node symptom.
As far as the effect of frequent nighttime awakenings on temping - to be perfectly honest, one doesn't often see temperatures all that disturbed by frequent awakenings. It's perhaps counter-intuitive since that's most definitely contrary to the rules of charting. However, the PATTERN of a series of low temps leading up to ovulation followed by a series of post-ovulation high temperatures is still usually visible in most cases. And ultimately it's the pattern that's important not the actually temperature.
Now, that's not going to be the case for everyone - some women's temperatures are VERY effected by nighttime awakenings or inadequate sleep. So, I would advise you to give it a try and see if the bi-phasic pattern is still visible.
And to drive this point again, (as PolkaDotMom pointed out) it's the cervical fluid, vaginal sensation, etc that are going to tell you that ovulation is approaching. Temps merely confirm that ovulation happened (past tense). So - as you approach ovulation and you start to notice ANY cervical fluid, you'll know that you're potentially entering a fertile phase.
Let me know if you'd like more resources on this. I've certainly written about it - as well as charting in the post-partum period - but I don't want to overwhelm you :-)
